Add a script in bin directory that can be called manually to turn a
replica into a primary. Being able to turn a replica into a primary
is an absolutely necessary feature of replication. It's a necessary
step of a takoever procedure.

Questions remain for automatisation. One option is to provide a url
the user may simply interact with (clickable button ...) to trigger
the script, that may also be used automatically as part of a larger
takoever procedure.

Triggering the change to primary by editing the instance parameters
- such as by removing the replication-related parameters - does not
seem best: one immediate drawback is the uncertain propagation time
of instance parameters; another is the reliance on the availability
of the SlapOS master to trigger a usually time-sensitive operation.

Allow requesting a mariadb set-up to replicate another mariadb:
- bootstrap from a statically served backup file
- replicate from a primary mariadb

This service does on-the-fly modifications on the running mariadb that
can conflict with and break replication and are anyway unneeded in the
replica.

Maybe this service should be dropped entirely and its functionality be
implemented another way.

Use a generated password and publish its url.

Remove

```
[gcc:python2]
part = gcc-8.5
```

from neoppod/software-common.cfg and dream/software.cfg as it causes
gcc being pinned to a different version before and after rebootstrap
when the initial python version is not Python2.

This reverts dc91e5d4.

When use-ipv6 is enabled, make mariadb publish an url of the form:
  `mysql://user:password@[ipv6]:port/database`

instead of:
  `mysql://user:password@ipv6:port/database`

which results in the zope instances crashing during processing
due to urlparse.urlsplit failing to parse the url.

See merge request nexedi/slapos!1668

See merge request nexedi/slapos!1668

See merge request nexedi/slapos!1668

See merge request nexedi/slapos!1668

GDAL is a library, and thus it should not mess with global settings.
This was causing the logs to be flooded with deprecation messages.

See merge request !1674

The syntax to compare strings is

      STRING1 = STRING2
                     True if the strings are equal.
      STRING1 != STRING2
                     True if the strings are not equal.

STRING1=STRING2 is not a valid syntax for strings comparisons.

This is same fix as 6cf1769d (ERP5: fix handling of repozo restoration
failure, 2024-10-24) and also a fix to a wrong error message, because
this is not restoration script, it's backup script.

Fluentbit Tail input documentation[1] says that by default maximum buffer
size is 32K which turned out to be too small in practice because we hit
a situation where enb.xlog started to have lines with ~ 34K and so
fluentbit ingestion stopped to work with the following error in
fluentbit log:

    [2024/10/23 20:30:23] [error] [input:tail:tail.0] file=/srv/slapgrid/slappart19/srv/monitor/public/enb.xlog requires a larger buffer size, lines are too long. Skipping file.

-> Fix that by increasing max buffer size to 1M which seems to be high
   enough at least for now.

Maybe it will make sense to configure this as unlimited, but I'm not
sure if going as unlimited is universally a good idea.

[1] https://docs.fluentbit.io/manual/pipeline/inputs/tail

/cc @lu.xu, @jhuge, @tomo
/reviewed-by @paul.graydon
/reviewed-on nexedi/slapos!1672

As discussed on bb841a7b (comment 219278)
when using storage-path and passwd option, the storage file could not
be updated to the new format because of AttributeError _needs_migration.

This changes to no longer try to detect if the storage needs migration,
but just compare the expected content of the storage file during install
and overwrite the file if it is different.

This new approach also fix a behavior that re-running buildout with
storage-path option and a different passwd option did not update the
storage file. Now it is also updated.

( this also fixes a potential encoding problem on py2 )

fix a SyntaxWarning on py3.9

See merge request !1664

This test is using two connection one with a client to subscribe to a
topic and wait for message and another one with publish.single to
publish to the topic.
The test was failing from time to time because the publish might have
happened after the client was subscribed.

Refactor the test to use `loop` on the client to have more control
and be able to wait for the client to be subscribed using the
`on_subscribe` callback.

The test is also factorized, instead of having the same test twice for
IPv4 and IPv6, we pass the host as parameter.

See merge request !1665

from repozo doc:

> If a full backup is created, remove any prior full or incremental
> backup files (and associated metadata files) from the repository
> directory.

This solves a problem that after a pack some old repozo files were left
around, with this option they are automatically removed.

Products.TIDStorage was not ported to python3 and is not installed on
software-py3.cfg but the backup crontab expects tidstorage to be
present - as a result, it was silently failing to produce backups.

This brings minimal support to repozo backups on python3, without
Products.TIDStorage interraction and also extends software release test
to have a simple test checking that backups are produced and can be
restored.

Split the instances in two:
 - "default" instance is grafana, loki (for logs) and influxdb (for
metrics)
 - "agent" instance is telegraf collecting metrics and logs and sending
 it the the "default" instance.

Next steps will be that the agent becomes not used, instead the
slapos instances will be able to push metrics or logs directly, probably
using fluentbit and sending to either loki/influxdb or wendelin.

boot-image-url-select is used instead of default image being downloaded by the
software release.

If nothing is selected, the default boot-image-url-select is used, but not if
other way to obatin boot image is enabled.

The vm-img uses ISOs internally and let it handle them, thus qemu-kvm can be
just a component providing qemu machine.

Also nbd2-host and nbd2-port are asserted.