Drop EoL Debian 10 support

Drop EoL CentOS 7/8 support

Drop EoL Ubuntu 18.04

modulesync 9.4.0

modulesync 9.5.0-4-g2cf9dc0

This module that manage python needs python to be installed in order to
work properly under certain conditions.

When python is not installed on a node, the python_version fact does not
have a value.  When using `python::pyvenv` on such a system without a
specific version set, a call of the split() function on this unde value
cause an error te be raised:

```
   Error: Evaluation Error: Error while evaluating a Resource Statement, Evaluation Error: Error while evaluating a Function Call, The function 'split' was called with arguments it does not accept. It expects one of:
    (String str, String pattern)
      rejected: parameter 'str' expects a String value, got Undef
    (String str, Regexp pattern)
      rejected: parameter 'str' expects a String value, got Undef
    (String str, Type[Regexp] pattern)
      rejected: parameter 'str' expects a String value, got Undef
    (Sensitive[String] sensitive, String pattern)
      rejected: parameter 'sensitive' expects a Sensitive[String] value, got Undef
    (Sensitive[String] sensitive, Regexp pattern)
      rejected: parameter 'sensitive' expects a Sensitive[String] value, got Undef
    (Sensitive[String] sensitive, Type[Regexp] pattern)
      rejected: parameter 'sensitive' expects a Sensitive[String] value, got Undef (file: /etc/puppetlabs/code/environments/production/modules/python/manifests/pyvenv.pp, line: 48, column: 34) (file: /etc/puppetlabs/code/environments/production/modules/taiga/manifests/back/install.pp, line: 15) on node debian12-64-puppet7.example.com
```

When Python is not installed, the python_version fact is undef, but we
need to know which version of Python is going to be installed by the
module in order to use the proper command invocation for building
virtual envs.

This issue only occurs when the user use the system version of Python,
so add the default version of Python for supported operating systems
into Hiera and use that as a fallback when the version of Python is
unknown.

Fix bootstrapping `python::pyvenv` when Python is not installed

Drop EoL Ubuntu 20.04 support

Drop EoL FreeBSD 11/12 support

Release 8.0.0