feat(hybridcloud): add index to apitokenreplica

[mdtro]

In support of: #65941

Adds an index for the hashed_token column on ApiTokenReplica.

[github-actions]

This PR has a migration; here is the generated SQL for src/sentry/hybridcloud/migrations/0015_apitokenreplica_hashed_token_index.py ()

--
-- Create index hybridcloud_hashed__a93a8b_idx on field(s) hashed_token of model apitokenreplica
--
CREATE INDEX CONCURRENTLY "hybridcloud_hashed__a93a8b_idx" ON "hybridcloud_apitokenreplica" ("hashed_token");

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.31%. Comparing base (e9d1973) to head (698445d).
Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #66947      +/-   ##
==========================================
- Coverage   84.31%   84.31%   -0.01%     
==========================================
  Files        5309     5310       +1     
  Lines      237399   237405       +6     
  Branches    41058    41058              
==========================================
+ Hits       200172   200176       +4     
- Misses      37009    37011       +2     
  Partials      218      218              

Files	Coverage Δ
...rations/0015_apitokenreplica_hashed_token_index.py	100.00% <100.00%> (ø)
src/sentry/hybridcloud/models/apitokenreplica.py	97.50% <100.00%> (ø)

... and 9 files with indirect coverage changes