fix(tracemetrics): Bump metric buffer to 1k …

[k-fish]

Summary

We've been noticing some discards from clients for likely buffer reason (primarily on python, though fixing it on both sdks). Metrics were initially set to 100 to match logs but the size limit for a metric in relay is ~1000x less (~1-2kb at the moment) so the memory pressure should be fine (it'd cap in the single digit megabyte range).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.96%. Comparing base (104db8c) to head (8cb05b4).
⚠️ Report is 5 commits behind head on master.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5031      +/-   ##
==========================================
+ Coverage   83.94%   83.96%   +0.01%     
==========================================
  Files         178      178              
  Lines       17834    17834              
  Branches     3170     3170              
==========================================
+ Hits        14971    14974       +3     
+ Misses       1901     1899       -2     
+ Partials      962      961       -1     

Files with missing lines	Coverage Δ
sentry_sdk/_metrics_batcher.py	69.87% <100.00%> (ø)

... and 3 files with indirect coverage changes