feat(gocd): add grouped pipedream v3 snuba pipeline names

Pipedream v3 collapses deploy-snuba-{py,rs}-customer-{1,2,4,7} into
deploy-snuba-{py,rs}-st. Add the new st pipeline names to Slack feed
filters and Datadog region mappings. Keep old customer-* names for
backward compat during staged rollout.

Also remove dead deploy-snuba-{py,rs}-s4s entries (s4s test region was
removed in gocd-jsonnet).

Ref: getsentry/gocd-jsonnet#92

Author: mchen-sentry

src/brain/gocd/gocdDataDog/deployDatadogEvents.ts

@@ -229,6 +229,7 @@ export class DeployDatadogEvents {
       s4s: 'st-sentry4sentry',
       us: 'us',
       de: 'de',
+      st: 'st',
       'customer-1': 'st-goldmansachs',
       'customer-2': 'st-geico',
       'customer-3': 'st-zendesk-eu',

src/brain/gocd/gocdSlackFeeds/index.ts

@@ -57,15 +57,17 @@ const SDKS_PIPELINE_FILTER = ['deploy-release-registry'];
 const SNS_SAAS_PIPELINE_FILTER = [
   'deploy-snuba-py',
   'rollback-snuba-py',
-  'deploy-snuba-py-s4s',
   'deploy-snuba-py-us',
   'deploy-snuba-rs',
   'rollback-snuba-rs',
-  'deploy-snuba-rs-s4s',
   'deploy-snuba-rs-us',
 ];
 
 const SNS_ST_PIPELINE_FILTER = [
+  // Grouped pipedream v3 names
+  'deploy-snuba-py-st',
+  'deploy-snuba-rs-st',
+  // Per-region names (v2, kept for backward compat during staged rollout)
   'deploy-snuba-py-customer-1',
   'deploy-snuba-py-customer-2',
   'deploy-snuba-py-customer-4',