Switch to pure meson build system and adapt configuration for SlapOS
requirements.

Support multiarch env by simply linking from lib64.

Thanks to migration to json-in-xml serialisation some lower level bugs has
been discovered with value types in the profiles, so simply fix it.

default and kvm-cluster software types are now json-in-xml, so they accept
and return json-in-xml.

Update tests to show that xml and json-in-xml serialization works.

Note: There was invective to publish with pure XML serialisation, but it is
wrong idea because:

 1) serialisation in the software.cfg.json is provided for both ways
 2) requesting instances with given serialisation by profiles expect same
    serialisation

Request resilient instances with serialised, as they reply with json-in-xml.

These are not supposed to be executed directly

See merge request nexedi/slapos!1179

This reverts commit 4fa33dfc.

This patch is not complete, backporting full support of
`__{code,defaults}__` on Zope2 would require patching more, so we
decided to keep using func_code with ERP5 on Zope2 and to use
__code__ only with ERP5 on Zope4

Extend the upgrade tests to create data before the upgrade, to
confirm that this data can still be found after the upgrade.

This also extends the test to confirm that after upgrade, inituser
can still login, create content and find content created before and
after upgrade.

After 4fa33dfc (erp5: py3: `func_{code,defaults}` was replaced in
Python3 by `__{code,defaults}__`., 2022-04-25), this was no longer
the case, because during indexation, using existing scripts failed
with AttributeError __code__

There is no real control over port chosen by push/pull.

There is no reason to keep python2 compatibility, as python3 flavour of the
KVM software release is good enough.

Thanks to recent increased test coverage python3 compatibility issue was
spotted, and can be fixed.

That's nothing wrong with such small disk, and the default seems reasonable
enough.

external-disk-* parameters are fully tested, including it's special features
like keeping the image available even in case of dropping them from request
parameters.

See merge request nexedi/slapos!1173

See commit 37cf8a50.

Since
nexedi/slapos.core@a8917a3c
and slapos.core https://lab.nexedi.com/nexedi/slapos.core/tags/1.7.4 the
tap_ipv4_addr value is empty by default on the servers, especially test nodes.

To not rely on what is provided on the test environment simply mock the
configuration of the machine so that the test is able to prove profile
functionality.

The test does not require to download some enormous images, so provide small
empty qcow2 images, good enough to start the VM.

The problem has been introduced in 5da9c082
"kvm: Improve boot image url handling".

Note the internal usage of md5sum value as image name in the download config
creator.

pim-dm is a python3 only egg and re6st is a python2 only egg.

Deploy pim-dm egg inside a totally separated buildout in python3. 

See merge request nexedi/slapos!1161

See merge request nexedi/slapos!1170

Now the nat-rule-port always has the protocol name, see here:
https://lab.nexedi.com/nexedi/slapos/blob/9a886c4b0c6dd229564292eaa0ef2604fa857aea/software/kvm/instance-kvm.cfg.jinja2#L843

See merge request nexedi/slapos!1166