Added method "fallbackExceptionMessage" to customize fallback exception message

[ZhandosKz]

Q	A
Is bugfix?	❌
New feature?	✔️
Breaks BC?	❌

Added the ability to customize the critical error message for the handleFallbackExceptionMessage method.
Previously, customizing this message required completely overriding the handleFallbackExceptionMessage
method. This PR introduces the ability to customize the error text by overriding just one method:
fallbackExceptionMessage

[codecov]

Codecov Report

❌ Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.15%. Comparing base (985ff9e) to head (a039999).
⚠️ Report is 1 commits behind head on master.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
framework/base/ErrorHandler.php	0.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #20681      +/-   ##
============================================
- Coverage     78.15%   78.15%   -0.01%     
- Complexity    11565    11566       +1     
============================================
  Files           376      376              
  Lines         30727    30729       +2     
============================================
  Hits          24016    24016              
- Misses         6711     6713       +2     

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[samdark]

Looks alright to me. Please add a line for changelog.

[mspirkov]

I think there is a dock block missing here.
It's worth adding the @param annotation for $exception.