[FEATURE REQUEST] Deprecate the ``__utils__`` dunder.

[s0undt3ch]

Is your feature request related to a problem? Please describe.

The __utils__ dunder(salt loader) tries to provide easy access to Salt's utility modules.

Issues with this approach:

• Utility functions should not be available in dunders, they are utility functions.
• All utilities are compacted into <module>.<funcname>, which does not recurse into submodules.
• This kind of usage, is prone to memory leaks(because utilities were not coded to work within a salt loader context). See fix memory leak in utils/jinja.py #62007 and fix yamlloader.DuplicateKeyWarning leaking #62021

Potential problems if we remove __utils__:

• Utility functions aren't available in jinja templating for salt states.
  • They shouldn't, jinja uses it's own filters and Salt provides additional filters

Describe the solution you'd like
Completely remove support for __utils__

Describe alternatives you've considered
None.

[OrangeDog]

If it's being removed in 3006 then it needs to be deprecated in 3005.

[OrangeDog]

There's a SEP for this: saltstack/salt-enhancement-proposals#66

[s0undt3ch]

If it's being removed in 3006 then it needs to be deprecated in 3005.

The deprecation period, sadly, needs to be longer.