Give users classes for easier manual instrumentation.

[antonpirker]

We have internal classes for setting Span.op and to set correct names for Span.data/Span.attribute items. Make them public so users can use SpanAttr and SpanOp for better manual instrumentation.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.12%. Comparing base (84adbb7) to head (1ced048).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4668      +/-   ##
==========================================
+ Coverage   85.09%   85.12%   +0.03%     
==========================================
  Files         156      156              
  Lines       15797    15797              
  Branches     2671     2671              
==========================================
+ Hits        13442    13447       +5     
+ Misses       1578     1576       -2     
+ Partials      777      774       -3     

Files with missing lines	Coverage Δ
sentry_sdk/__init__.py	100.00% <ø> (ø)
sentry_sdk/api.py	90.29% <100.00%> (ø)

... and 4 files with indirect coverage changes