conditionally enable searching for alert groups via env var (#4287)

# What this PR does

re-enables the search for alert groups

## Which issue(s) this PR closes

Closes #2232

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## Checklist

- [x] Unit, integration, and e2e (if applicable) tests updated
- [x] Documentation added (or `pr:no public docs` PR label added if not
required)
- [x] Added the relevant release notes label (see labels prefixed w/
`release:`). These labels dictate how your PR will
    show up in the autogenerated release notes.

---------

Co-authored-by: Joey Orlando <[email protected]>
Co-authored-by: Joey Orlando <[email protected]>

src/models/alertgroup/alertgroup.ts

@@ -65,7 +65,7 @@ export class AlertGroupStore {
       params: {
         query: {
           ...incidentFilters,
-          search,
+          search: incidentFilters?.search || search,
           perpage: this.alertsSearchResult?.page_size,
           cursor: this.incidentsCursor,
           is_root: true,