Add option to enable debug mode in Log4j2 integration.

[maciejwalkowiak]

📜 Description

Add option to enable debug mode in Log4j2 integration.

💡 Motivation and Context

Fixes #1488
Simplify debugging in cases like https://stackoverflow.com/questions/67690759/why-does-sentry-not-work-with-log4j2-for-me

💚 How did you test it?

Unit tests.

📝 Checklist

• I reviewed the submitted code
• I added tests to verify the changes
• I updated the docs if needed
• No breaking changes

[codecov-commenter]

Codecov Report

Merging #1492 (411cd0a) into main (8010018) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##               main    #1492   +/-   ##
=========================================
  Coverage     75.65%   75.66%           
  Complexity     1929     1929           
=========================================
  Files           191      191           
  Lines          6598     6600    +2     
  Branches        666      666           
=========================================
+ Hits           4992     4994    +2     
  Misses         1280     1280           
  Partials        326      326           

Impacted Files	Coverage Δ
...src/main/java/io/sentry/log4j2/SentryAppender.java	85.18% <100.00%> (+0.37%)	⬆️

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