This is a big changes for users, now typing "python" on the command line
will use system python if it exists or fail with "command not found".

`python3` is set to the SlapOS python from Theia software release.
Recommended approach for python users is either to get used to type
`python3` or to create a virtualenv and use it. With the virtualenv,
they can also install pylint or other linters, so this might be the
best thing to do.

This solves two problems:

First problem is that it makes the embedded SlapOS always have a python
interpreter as `python` in $PATH, which is not always the case in other
SlapOS usage and can hide problems that would cause a software to build
successfully in Theia but not in "bare metal" SlapOS.

Second problem problem is that on python was a interpreter from pygolang
and it is not perfect regarding line edition at least on python 3.8, as
we can observe in this session:

run python and type "something":

```
Python 3.8.13 (default, Sep  6 2022, 10:45:07)
[GCC 8.5.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> something
             ^ cursor is here, as expected
```

type Ctrl+A to go to beginning of line:

```
Python 3.8.13 (default, Sep  6 2022, 10:45:07)
[GCC 8.5.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> something
    ^ expected cursor position
^ actual cursor position
```

likewise, type Ctrl+E to go to end of line:

```
Python 3.8.13 (default, Sep  6 2022, 10:45:07)
[GCC 8.5.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
(InteractiveConsole)
>>> something
             ^ expected cursor position
         ^ actual cursor position
```

We should not use $PYTHON, because this implicitly depends on the
python version that was used when the shared part is installed, leading
to this kind of problematic scenarios:
 - install the part from a python2.7 software, this creates scripts
  with "python2.7" in shebang line
 - install a python3 software referencing glib, it uses the shared
  part that was installed with python2, but "python2.7" is not in $PATH

By referencing the part explicitly, it becomes part of the signature
of the part, so a software on python2 and a software on python3 will
use a different version of the shared part.

945a2e97 (proxysql: bundled libinjection needs Python 2, 2021-12-23)
addressed the problem that proxysql was using system python, by placing
slapos' python in $PATH, but it added it after default $PATH, which
made proxysql use system python if available and only fallback to
slapos' python.
This changes the order of $PATH entries to always use slapos' python

python or python2 is system python, which we want to avoid

Co-authored-by: Kazuhiko SHIOZAKI <kazuhiko@nexedi.com>

This reverts commit b2db18a0cb672204ff1dd9bc759934b332d433f5.

This contain the fix for go 1.16 that we backported, so we can use
upstream repository again

For now this still have to be enabled with a config like this in a .conf
file in srv/telegraf/extra-config/  :

    [[inputs.execd]]
      name_override = "slapos"
      # this needs sudo when using can not access supervisor socket, like when being installed in root slapos
      command = ["/usr/bin/sudo", "$SOFTWARE_DIR/go.work/bin/telegraf-input-slapos", "-config", "/path/to/slapos.conf"]

/path/to/slapos.conf would contain something like this:

    [[inputs.slapos]]
      ## Folder where partitions are located
      instance_root = "/srv/slapgrid/"

      ## filepath.Glob pattern to look for recursive instances
      recursive_instance_glob_pattern = "*/srv/runner/inst*/"

      ## Path of supervisor socket, relative to instance root
      socket_name = "sv.sock"

This version has a new sql input, that can be used to get metrics from sql
queries.

starting coverage in runUnitTest was too late, coverage has to be
started before anything is imported for correct reporting

Since slapos.core!436 requesting with `--parameters-file` requires
that a JSON schema exists at <sr-url>.json for the requested SR.

Missing trailing /

See nexedi/slapos@5e1ff2de

zlib source url has been moved. Please see issue
https://github.com/madler/zlib/issues/649 for reference.

See merge request nexedi/slapos!1276