chore: Register flag that consolidates all span-first UI

[shruthilayaj]

Create an options backed flag for all starfish UI so we can enable them

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.71%. Comparing base (5b88c7e) to head (d71be76).
Report is 18 commits behind head on master.

❗ Current head d71be76 differs from pull request most recent head 9b24574. Consider uploading reports for the commit 9b24574 to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #68911       +/-   ##
===========================================
+ Coverage   68.94%   79.71%   +10.76%     
===========================================
  Files        6422     6424        +2     
  Lines      284528   284737      +209     
  Branches    49021    49051       +30     
===========================================
+ Hits       196175   226981    +30806     
+ Misses      87948    57357    -30591     
+ Partials      405      399        -6     

Files	Coverage Δ
src/sentry/conf/server.py	89.22% <ø> (ø)
src/sentry/features/temporary.py	100.00% <100.00%> (ø)
src/sentry/options/defaults.py	100.00% <100.00%> (ø)

... and 1400 files with indirect coverage changes