slapos.core now depends on PyYAML and jsonschema

This upgrade fixes deadlock when new context is created from
already-canceled parent[1]. It also comes with other minor enhancements
and fixes needed e.g. for `zodb restore`[2].

[1] nexedi/pygolang@58d4cbfe
[2] https://pypi.org/project/pygolang/#pygolang-change-history

json-c, memcached and xpdf are still maintained but current
buildout.cfg are not useful if we want to ship a new version.

Keep compatibility with the default webrunner configuration.

Prevent unexpected instance deletion.

See merge request nexedi/slapos!1094

It appears no longer needed to use LD_LIBRARY_PATH to ensure the
correct runtime path resolution of libsecret in theia's `keytar`
component. Also LD_LIBRARY_PATH was leaking into theia's environment
and affecting tests launched from within theia.

This reverts commit 681ec188.

See merge request nexedi/slapos!1096

Always format the partitions to ensure the slapformat configuration is
valid, because the constructor overwrites it with invalid values.

We need a valid configuration so that `slapos node format` works,
and we need `slapos node format` for the resiliency import script.

No need for the full URL here

This will force a password reset

Aggregate monitoring URLs from the main theia, clones and PBS.

Also add monitor-setup-url to the parameters published by the PBS.

32fbf0d4 (recipe/postgres: support non standard port, 2021-11-12)
broke support for empty port, it was generating config file with
`port = ` , which is an invalid config file syntax for postgresql.