Throw exception when fixture not found rather than ignoring.

[borgou]

Q	A
Is bugfix?	✔️
New feature?	❌
Breaks BC?	✔️
Fixed issues	when provided fixture not found(wrong namespace or use namespace like app/tests/unit/fixture, etc), there will be no warning.

[what-the-diff]

PR Summary

• Enhanced Error Handling for Missing Fixtures
  The new changes provide feedback when the system is unable to find the specified 'fixtures' or test data. The system will now throw a clear error message if you try to find fixtures in a namespace, or a specified area of the software, where none exist. This will aid in quicker error identification and resolution.

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (af1858c) 48.00% compared to head (c155fc8) 48.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #20047      +/-   ##
==========================================
- Coverage   48.00%   48.00%   -0.01%     
==========================================
  Files         445      445              
  Lines       43887    43888       +1     
==========================================
  Hits        21069    21069              
- Misses      22818    22819       +1     

Files	Coverage Δ
...ramework/console/controllers/FixtureController.php	0.00% <0.00%> (ø)

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[bizley]

Please add a changelog line, thanks.