[master] Speed up salt.matcher.confirm_top by using __context__

[vzhestkov]

What does this PR do?

In case of having complex top.sls with a list of different matchers based on grains/pillars etc. it could be possible that salt will reload matchers again and again for all of the possible matches in top.sls, this fix is intended to speed up the pillar renderer by reusing he matchers loaded once and stored in the __context__.

Example:
with top.sls like the following:

base:
...
  'grain_name_A:value_X':
    - match: grain
    - subdir.X

  'grain_name_A:value_Y':
    - match: grain
    - subdir.Y
...

In case if the number of matching rules significant it could take unexpected amount of time due to loading the matchers on each rule.

What issues does this PR fix or reference?

Tracks: https://github.com/SUSE/spacewalk/issues/23526

Previous Behavior

If there is a list of different matches in top.sls for pillar it could take much time to render pillar data on _pillar calls from the minions.

New Behavior

Each next call for rendering the pillar will reuse the matchers from the __context__ so it will significantly speed up the calls.

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

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