To add a Database, user should request a slave instance. Each slave
instance is a database.

- Destroy slave database if slave instance was destroyed

- Update and remove slave database only on master mariadb

- Allow to create database slave with character sets and collate options

- Generate slave database password if not set

The added zlib dependency is for the bundled prometheus-cpp, else:

CMake Error at .../cmake-3.18/.../share/cmake-3.18/Modules/FindPackageHandleStandardArgs.cmake:165 (message):
  Could NOT find ZLIB (missing: ZLIB_LIBRARY ZLIB_INCLUDE_DIR)
Call Stack (most recent call first):
  .../cmake-3.18/.../share/cmake-3.18/Modules/FindPackageHandleStandardArgs.cmake:458 (_FPHSA_FAILURE_MESSAGE)
  .../cmake-3.18/.../share/cmake-3.18/Modules/FindZLIB.cmake:115 (FIND_PACKAGE_HANDLE_STANDARD_ARGS)
  pull/CMakeLists.txt:9 (find_package)

So far, it "worked" because Python 2 was found on the system.
Not the case anymore in our Debian 11 test nodes.

Preserve "disk" group to stay in /etc/group as explained in
nxdtest@6f75fa90 because
slapos.core tests use this.

See merge request !1107

This reverts commit 86707a66.

This reverts commit fc7928fb.

Now that `slapos request` understands `json-in-xml` serialisation and
automatically unwraps the instance connexion parameters when printing
them, we need to adapt how the ERP5 test parses that output.

See merge request !1069

Keep old version for libxslt.

Keep old version for compatbility with kvm.

5s is the historical default tic periodicity, but 1s is typically used in
production instances. 1s periodicity should improve validation node
reactivity in all cases, and general activity reactivity in instances with
few processing nodes (like development instances).

Reading this spec, we probably want to change
```
  entry_run = 'from %s import %s; %s()' % (mod, func, func)
```
to
```
  entry_run = 'import sys; from %s import %s; sys.exit(%s())' % (mod, func, func)
```
to follow
https://packaging.python.org/en/latest/specifications/entry-points/#use-for-scripts
, this is also what `zc.recipe.egg` does.

/reviewed-by @kirr
/reviewed-on !1108

In e328aa49 (component/nxdtest: Prepare for nxdtest!13)
I reworked how nxdtest script is generated and splitted it into nxdtest itself
and .nxdtest.pyexe python interpreter, so that sys.executable could be used to
correctly spawn other python scripts:

    3) rework how nxdtest script is generated and split it into .nxdtest.pyexe and
       nxdtest itself. .nxdtest.pyexe is python interpreter via which nxdtest is run.
       This interpreter has all eggs required by nxdtest in sys.path, so that
       nxdtest could spawn its trun.py via sys.executable. If we don't care to have
       properly setup sys.executable, trun.py will fail when importing any module that
       nxdtest.py could already successfully import.

       Initially I tried to workaround this issue via adjusting $PYTHONPATH <-
       sys.path in main nxdtest script, but @jerome points out that, $PYTHONPATH,
       if set, also affects processes that trun.py spawns, which is not good:

       !1095 (comment 146799)

       -> so fix this via running nxdtest via environment where sys.executable is
       properly setup python interpreter with path for all eggs that nxdtest has
       access to.

       Because we already have half-way workarounds for similar problem in several
       places, and because running a script with correctly setup sys.executable is
       generally better, I would say it should be a good idea to rework
       zc.recipe.egg:scripts to generate all scripts to work this way, but I do not
       want to fight about it.

       So let's leave this scheme nxdtest-specific for now.

This patch addresses the last paragraph and provides a general pyprog buildout
macro that could be used to generate python script for any entry point to run
with correctly set sys.executable.

/reviewed-by @jerome
/reviewed-on !1108

This upgrade

- teaches nxdtest to run each testcase with its own /tmp and /dev/shm to
  detect after each test run leaked temporary files, leaked mount
  entries, to isolate different test runs from each other, and to provide
  tmpfs on /tmp for every test.

  nexedi/nxdtest!13

- teaches nxdtest to propagate cancellation to spawned test jobs, so
  that whenever user cancels corresponding test run in ERP5 UI, nxdtest
  stops promptly. This should be most useful for long-running tests like
  SlapOS.SoftwareReleases.IntegrationTest-* which before had to be
  waited for for hours to complete even after cancelling test run in ERP5.

  nexedi/nxdtest!14

Pytest-mock is added because it becomes dependency to test nxdtest
itself.

Several places pin mock egg individually. There are pins to `mock = 3.0.5`
and pins to `mock = 2.0.0:whl`. Mock 3.0.5 is the last version that
supports Python2 and can be considered as "current" in our context today.

For nxdtest we are going to add pytest-mock, which depends on the mock,
which, if not consolidated, will need to add another `mock = 3.0.5`
somewhere.

-> Stop doing that and move mock pinning into stack/slapos.cfg.
This way it will be even easier for upcoming Python3 support, because in
stack/slapos.cfg we can add per-Python3 [versions] with pins adjusted as
needed for py3, but all still in one single place.

Leave `mock = 2.0.0:whl` pins intact to be updated when needed by
maintainers of corresponding software releases:

    software/slapos-sr-testing/software.cfg:mock = 2.0.0:whl
    software/slapos-testing/software.cfg:mock = 2.0.0:whl
    software/wendelin/software-kerastensorflow.cfg:mock = 2.0.0:whl

IMS and MME are in the same instance, but there is only one TUN
per instance. IMS is not crucial right now so we temporarily remove it
until we implement a clean solution.

We were trying to patchelf a file that apparently exists when Theia
is compiled on Debian 8, 10 and 11, but not on Debian 9.

See merge request nexedi/slapos!1105

Include the hash of all parameters related to the embedded instance
as a comment in the standalone script, so that if the hash changes,
the script and its own hash change as well, and standalone service
will be restarted.

Generate standalone script in instance-theia.cfg.jinja.in instead of
in software.cfg, avoiding the need to forward all the parameters.

Include the hash of the relevant parameters in the abstract socket path,
so that when changing these instance parameters the promise waits until
the standalone service has taken the new parameters into account.

Change "Embedded Instance" to "embedded_instance", and rename existing
"Embdded Instance" into "embedded_instance" for compatibility.