update release threshold api routes

[nhsiehgit]

rather than conflicting with the existing /releases/ routes
opt to simply have a separate url to manage release thresholds

NOTE: none of these routes are being utilized atm

[github-actions]

🚨 Warning: This pull request contains Frontend and Backend changes!

It's discouraged to make changes to Sentry's Frontend and Backend in a single pull request. The Frontend and Backend are not atomically deployed. If the changes are interdependent of each other, they must be separated into two pull requests and be made forward or backwards compatible, such that the Backend or Frontend can be safely deployed independently.

Have questions? Please ask in the #discuss-dev-infra channel.

[codecov]

Codecov Report

Merging #58177 (bf9b566) into master (de3a4e8) will increase coverage by 0.65%.
Report is 12 commits behind head on master.
The diff coverage is 69.23%.

@@            Coverage Diff             @@
##           master   #58177      +/-   ##
==========================================
+ Coverage   78.39%   79.05%   +0.65%     
==========================================
  Files        5135     5135              
  Lines      223461   223465       +4     
  Branches    37624    37626       +2     
==========================================
+ Hits       175185   176659    +1474     
+ Misses      42629    41150    -1479     
- Partials     5647     5656       +9     

Files	Coverage Δ
...dpoints/organization_events_root_cause_analysis.py	96.19% <100.00%> (+0.07%)	⬆️
...lease_thresholds/release_threshold_status_index.py	84.25% <ø> (ø)
src/sentry/api/urls.py	100.00% <ø> (ø)
static/app/components/avatar/avatarList.tsx	90.90% <ø> (ø)
...c/sentry/integrations/slack/views/link_identity.py	86.36% <50.00%> (ø)
...ns/notifications/activity/new_processing_issues.py	89.79% <50.00%> (ø)
src/sentry/api/serializers/models/project.py	95.95% <71.42%> (-0.39%)	⬇️

... and 128 files with indirect coverage changes

[sentaur-athena]

@nhsiehgit can you remind me the object hierarchy here? Makes sense if we fetch the same release threasholds for all releases in an org. If we have different thresholds for each realease something like releases/{release_id}/threshods makes sense. If we have one threshold per project then something like projects/{project_id}/release-thresholds makes sense

[nhsiehgit]

@sentaur-athena Yup - thresholds are per project/env
So org/thresholds would get you all the threshlods for all projects of that org.