feat: testOnly events

[mdjastrzebski]

Summary

Resolves #1738

Provides support for testOnly_onXxx events to Fire Event and User Event, which together with software-mansion/react-native-gesture-handler#3357 allow for RNGH Pressable to work with RNTL.

Test plan

Addent automatic tests. Validate after RNGH PR is merged and published.

CC: @latekvo @sidferreira

[codecov]

Codecov Report

Attention: Patch coverage is 95.23810% with 2 lines in your changes missing coverage. Please review.

Project coverage is 95.48%. Comparing base (315afca) to head (9ef72d5).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/event-handler.ts	94.87%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1741      +/-   ##
==========================================
- Coverage   95.63%   95.48%   -0.15%     
==========================================
  Files          92       93       +1     
  Lines        5195     5205      +10     
  Branches      879      564     -315     
==========================================
+ Hits         4968     4970       +2     
- Misses        227      235       +8     

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