Add data field to SentrySpan.

[maciejwalkowiak]

📜 Description

Add data field to SentrySpan.

💡 Motivation and Context

Fixes #1538

💚 How did you test it?

JSON serialization 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 #1555 (6ad3559) into main (007cf3d) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##               main    #1555      +/-   ##
============================================
+ Coverage     76.02%   76.03%   +0.01%     
- Complexity     1953     1955       +2     
============================================
  Files           192      192              
  Lines          6760     6764       +4     
  Branches        676      676              
============================================
+ Hits           5139     5143       +4     
  Misses         1294     1294              
  Partials        327      327              

Impacted Files	Coverage Δ
...y/src/main/java/io/sentry/protocol/SentrySpan.java	96.29% <100.00%> (+0.64%)	⬆️

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