Allow selecting any service name, transaction type (where appropriate), and environment when creating and editing rules, both in APM and Stack Management.
- Create /internal/apm/suggestions endpoint that uses `terms_enum`
- Use combo box for environment, service name, and transaction type with suggestions endpoint on all alerts
- Remove "Go to APM" callouts on new alert creation
- Wrap calls to `createCallApmApi` in alert triggers with `useEffect`
- Use `getEnvironmentLabel` for value in environment field expression
- Make all `AlertParams` fields optional (except in latency threshold alert)
- Add e2e tests for creating an alert
- Remove `NewAlertEmptyPrompt` component and `isNewApmRuleFromStackManagement` helper
- Replace `maxServiceEnvironments` and `maxServiceSelections` config options with `maxSuggestions` advanced setting.
![CleanShot 2021-09-28 at 10 35 58](https://user-images.githubusercontent.com/9912/135119948-e247615a-d235-4feb-b197-b803f165ad1e.gif)
Fixes#106786