fix(hc): Silo fixes for alert rule actions

[RyanSkonnord]

Restore #57949, which was reverted by #58091. Fix SENTRY-16NH.

Adapt OrganizationAlertRuleAvailableActionIndexEndpoint and get_available_action_integrations_for_org to run in the region silo.

Introduce a prepare_sentry_app_components method to AppService. Remove the method of the same name from the SentryAppInstallation model. (It previously dispatched to the same module-level function that AppService now calls. The model method was called nowhere else.)

Mark OrganizationAlertRuleAvailableActionIndexEndpointTest as stable. Change setup to pass RPC models as needed.

[RyanSkonnord]

Code originally reviewed in #57949 is in 08be39d.

See 93c8f9c for new changes.

[codecov]

Codecov Report

Merging #58185 (e92098c) into master (3389169) will decrease coverage by 0.01%.
Report is 11 commits behind head on master.
The diff coverage is 85.29%.

@@            Coverage Diff             @@
##           master   #58185      +/-   ##
==========================================
- Coverage   79.05%   79.05%   -0.01%     
==========================================
  Files        5135     5135              
  Lines      223458   223478      +20     
  Branches    37620    37625       +5     
==========================================
+ Hits       176661   176675      +14     
+ Misses      41146    41145       -1     
- Partials     5651     5658       +7     

Files	Coverage Δ
src/sentry/incidents/logic.py	91.44% <100.00%> (-0.02%)	⬇️
...try/models/integrations/sentry_app_installation.py	97.89% <100.00%> (+0.86%)	⬆️
src/sentry/services/hybrid_cloud/app/impl.py	86.06% <100.00%> (+0.59%)	⬆️
src/sentry/services/hybrid_cloud/app/model.py	94.50% <100.00%> (+0.06%)	⬆️
src/sentry/services/hybrid_cloud/app/serial.py	90.00% <100.00%> (+1.76%)	⬆️
src/sentry/services/hybrid_cloud/app/service.py	80.00% <75.00%> (-0.27%)	⬇️
.../organization_alert_rule_available_action_index.py	92.98% <73.33%> (-2.94%)	⬇️

... and 14 files with indirect coverage changes

[markstory]

Looks good to me.