PROBLEM: The builtin python3 provider cannot auto-detect python3.12
when g:python3_host_prog is not set. As a result, when python3 on $PATH
is currently python 3.12, neovim will fail to load python3 provider
and result in `has("python3") == 0`, e.g.,
"Failed to load python3 host. You can try to see what happened by ..."

ROOT CAUSE: the `system()` call from `provider#pythonx#DetectByModule`
does not ignore python warnings, and `pkgutil.get_loader` will print
a warning message in the very first line:
```
<string>:1: DeprecationWarning: 'pkgutil.get_loader' is deprecated and
slated for removal in Python 3.14; use importlib.util.find_spec() instead
```

SOLUTION:
- Use `importlib.util.find_spec` instead (python >= 3.4)
- Use `-W ignore` option to prevent any potential warning messages

- list(filter(lambda x: x != "", sys.path))
+ [p for p in sys.path if p != ""]

Change missing provider plugins from errors to warnings for python and
perl. Also give proper advice under the ADVICE section instead of just
the errors.

These versions of python has reached End-of-life. getting rid
of python2 support removes a lot of logic to support two
incompatible python versions in the same version.

"3.10" < "3.3" but v3.10 > v3.3
Fixes #14586

Certain values of 'wildignore', .e.g `*/node_modules/**`, would make the
provider checks not find the right executables.

Fixes https://github.com/neovim/neovim/issues/14388

Python 3.9 was released, so we need to add support for the upcoming Python 3.10.
Python 3.5 and earlier reached their end-of-life.

PEP 478: Python 3.5  Release Schedule: https://www.python.org/dev/peps/pep-0478
PEP 596: Python 3.9  Release Schedule: https://www.python.org/dev/peps/pep-0596
PEP 619: Python 3.10 Release Schedule: https://www.python.org/dev/peps/pep-0619

When UV_OVERLAPPED_PIPE was used for the pipe passed to the child process, a
problem occurred with the standard input of the .Net Framework application
(#11809). Therefore, add the overlapped option to jobstart() and change it so
that it is set only when necessary

3.9's scheduled for beta release today.
https://www.python.org/dev/peps/pep-0596/