feat(assert/unstable): allow asserting predicates against thrown/rejected errors

[lionel-rowe]

Closes #6592.

This also allows regexes to be used with assertThrows and assertThrows, for consistency with assertIsError.

Clean diffs against cloned versions of the stable files: d470af4...lionel-rowe:std:throws-rejects-predicate

[codecov]

Codecov Report

Attention: Patch coverage is 98.11321% with 3 lines in your changes missing coverage. Please review.

Project coverage is 94.75%. Comparing base (096f0be) to head (477ecca).

Files with missing lines	Patch %	Lines
assert/unstable_rejects.ts	95.38%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #6629    +/-   ##
========================================
  Coverage   94.74%   94.75%            
========================================
  Files         583      586     +3     
  Lines       46478    46637   +159     
  Branches     6523     6572    +49     
========================================
+ Hits        44036    44191   +155     
- Misses       2399     2403     +4     
  Partials       43       43            

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