Do not insert local paths before standard library paths

[marmarek]

What does this PR do?

Inserting local paths like salt/utils before standard library makes many modules in utils conflict with standard library. This is especially relevant for salt-ssh. For example salt.utils.configparser - it tries to import configparser from stdlib, but due to salt/utils path being prepended to sys.path, it imports itself:

[ERROR   ] Failed to import fileserver gitfs, this is due most likely to a syntax error:
Traceback (most recent call last):
  File "/var/tmp/.root_dd8a91_salt/pyall/salt/loader/lazy.py", line 902, in _load_module
    self.run(spec.loader.exec_module, mod)
    ~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/var/tmp/.root_dd8a91_salt/pyall/salt/loader/lazy.py", line 1365, in run
    return self._last_context.run(self._run_as, _func_or_method, *args, **kwargs)
           ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/var/tmp/.root_dd8a91_salt/pyall/salt/loader/lazy.py", line 1380, in _run_as
    ret = _func_or_method(*args, **kwargs)
  File "<frozen importlib._bootstrap_external>", line 1023, in exec_module
  File "<frozen importlib._bootstrap>", line 488, in _call_with_frames_removed
  File "/var/tmp/.root_dd8a91_salt/pyall/salt/fileserver/gitfs.py", line 52, in <module>
    import salt.utils.gitfs
  File "/var/tmp/.root_dd8a91_salt/pyall/salt/utils/gitfs.py", line 31, in <module>
    import salt.utils.configparser
  File "/var/tmp/.root_dd8a91_salt/pyall/salt/utils/configparser.py", line 7, in <module>
    from configparser import *  # pylint: disable=no-name-in-module,wildcard-import,unused-wildcard-import
    ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/var/tmp/.root_dd8a91_salt/running_data/var/cache/salt/minion/extmods/utils/configparser.py", line 12, in <module>
    class GitConfigParser(RawConfigParser):
                          ^^^^^^^^^^^^^^^
NameError: name 'RawConfigParser' is not defined

On the other hand, places that try to use such duplicated modules from utils, import them via full name (as seen above: import salt.utils.configparser).

Change the insert_system_path() function to not insert paths before standard library.

What issues does this PR fix or reference?

Fixes #68755

Previous Behavior

Several state modules (including pkg.installed on RedHat-based distro) are unavailable via salt-ssh

New Behavior

No import conflict, pkg.installed works.

Merge requirements satisfied?

[NOTICE] Bug fixes or features added to Salt require tests.

• Docs
• Changelog - https://docs.saltproject.io/en/master/topics/development/changelog.html
• Tests written/updated

Commits signed with GPG?

Yes

[marmarek]

The failure I get is:

_______________________________________________________________________________________ test_allow_tgt _______________________________________________________________________________________

salt_run_cli = SaltRun(id='master-V1jApH', config_file='/tmp/stsuite/master-V1jApH/conf/master', config_dir='/tmp/stsuite/master-V1jA...slow_stop=True, timeout=30, script_name='/tmp/stsuite/scripts/cli_salt_run.py', base_script_args=[], display_name=None)
salt_minion = SaltMinion(id='minion-TwcZ68', config_file='/tmp/stsuite/minion-TwcZ68/conf/minion', config_dir='/tmp/stsuite/minion-T...=[], extra_cli_arguments_after_first_start_failure=['--log-level=info'], display_name="SaltMinion(id='minion-TwcZ68')")

    @pytest.mark.usefixtures("pillar_tree", "master_id", "salt_minion_id")
    def test_allow_tgt(salt_run_cli, salt_minion):
        tgt = salt_minion.id
        fun = "test_fun"
    
        ret = salt_run_cli.run("mine.get", tgt, fun)
>       assert ret.data == {salt_minion.id: "hello test"}
E       AssertionError: assert {} == {'minion-TwcZ68': 'hello test'}
E         
E         Right contains 1 more item:
E         {'minion-TwcZ68': 'hello test'}
E         
E         Full diff:
E         + {}
E         - {
E         -     'minion-TwcZ68': 'hello test',
E         - }

Is it related to my change? I think it isn't given I got it also in https://github.com/saltstack/salt/actions/runs/22261566839, which doesn't include this change.