Adding no-op X509_TRUST_cleanup for select application compatibility

[kingstjo]

Description of changes:

• Re-implements X509_TRUST_cleanup() as a No-Op function after previous removal
• Function was removed in commit #74c1f2a but is needed for select consuming applications
• Added documentation explaining AWS-LC's different approach to trust settings

Testing:

• No regression testing needed (No-Op implementation)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and the ISC license.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 79.04%. Comparing base (5054cf0) to head (809580f).

Files with missing lines	Patch %	Lines
crypto/x509/x509_trs.c	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2257      +/-   ##
==========================================
- Coverage   79.05%   79.04%   -0.01%     
==========================================
  Files         612      612              
  Lines      106517   106519       +2     
  Branches    15052    15053       +1     
==========================================
- Hits        84204    84196       -8     
- Misses      21660    21670      +10     
  Partials      653      653              

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