Add unit tests for filters

[WarLikeLaux]

Q	A
Is bugfix?	❌
New feature?	❌
Breaks BC?	❌
Fixed issues

What does this PR do?

Add unit tests for AccessControl orchestration, VerbFilter, and AccessRule::matchCallback.

Before / After

File	Tests	Methods	Lines	MSI
AccessControl.php	0 → 14	0/3 → 3/3	0/25 (0%) → 25/25 (100%)	— → 93% (27/29)
VerbFilter.php	0 → 13	0/2 → 1/2	0/14 (0%) → 13/14 (93%)	— → 92% (12/13)
AccessRule.php	31 → 35	7/7	49/49 (100%)	— → 89% (92/103)

VerbFilter line 87 (events() method) is covered only through behavior attachment, not direct beforeAction() calls.

Escaped mutants (all equivalent)

AccessControl.php (2): MethodCallRemoval - L104, parent::init() removal. ProtectedVisibility - L154, visibility change.

VerbFilter.php (1): ConcatOperandRemoval - L112, exception message text.

AccessRule.php (11): ProtectedVisibility ×6 - L192, L201, L222, L264, L294, L303, always equivalent. ReturnRemoval ×3 - L214, L257, L287, return false → implicit null, falsy either way in boolean && chain inside allows(). UnwrapArrayMerge - L227, array_merge → direct assign not caught because can() mock returns same value for all items. LogicalAnd - L249, && → || in roleParams callable check produces same result for all tested input types (arrays, closures, callable objects).

Changelog not required, because no source files changed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.24%. Comparing base (37b6e7b) to head (528d62c).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #20774      +/-   ##
============================================
+ Coverage     80.13%   80.24%   +0.10%     
  Complexity    11533    11533              
============================================
  Files           374      374              
  Lines         30206    30206              
============================================
+ Hits          24207    24238      +31     
+ Misses         5999     5968      -31     

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