[master] Access pillar data while rendering pillars

[dwoz]

What does this PR do?

Pillar dunder is now available in extension modules during pillar render

Fixes: #65724

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

[frebib]

An interesting thought I had was that it's probably not even necessary to call salt.loader.minion_mods() to update the pillar object- we could simply replace the pillar in the pack and save the overhead of reloading all of the modules

>>> mods = salt.loader.minion_mods(opts, utils=utils)
>>> mods.pack["__pillar__"]
{'foo': 'bar', 'baz': 123}
>>> mods["pillar.get"]("foo")
'bar'
>>> mods["pillar.get"]("baz")
123
>>> mods["pillar.get"]("aaaaaa")
''

>>> opts["pillar"].update({"aaaaaa": 5555})
>>> mods.pack["__pillar__"] = opts["pillar"]
>>> mods["pillar.get"]("aaaaaa")
5555

[frebib]

Yep, I can confirm that with some tweaks this does solve the same problem as my patch, but in a much less shitty way. Thanks @dwoz
I'd love to see this in 3007

[twangboy]

Looks like the failing tests are valid