feat(insights): Granular backend feature flags

[gggritso]

Sibling to #71821 but on the backend. Basically, disable the Aggregate Span Waterfall and Span Duration Comparison features if the organization doesn't have access to Insights modules (AKA span metrics!)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.91%. Comparing base (36312a7) to head (aba1bdd).
Report is 17 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #71823      +/-   ##
==========================================
+ Coverage   72.59%   77.91%   +5.31%     
==========================================
  Files        6562     6557       -5     
  Lines      292268   292165     -103     
  Branches    50485    50453      -32     
==========================================
+ Hits       212175   227640   +15465     
+ Misses      73722    58273   -15449     
+ Partials     6371     6252     -119     

Files	Coverage Δ
...sentry/api/endpoints/organization_event_details.py	91.13% <100.00%> (ø)
...ry/api/endpoints/organization_spans_aggregation.py	93.18% <100.00%> (+1.13%)	⬆️

... and 994 files with indirect coverage changes

[wmak]

lgtm