[APM Plugin - Browser] Migrate authc.getCurrentUser usage to coreStart.security (#187192)

Part of https://github.com/elastic/kibana/issues/186574

## Summary

This PR migrates the method to access an APM Plugin view model field,
which consumes `authc.getCurrentUser`, to use `coreStart.security`.

Background: This PR serves as an example of a plugin migrating away from
depending on the Security plugin, which is a high priority effort for
the last release before 9.0.

### Checklist

Delete any items that are not applicable to this PR.

- [ ] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios

x-pack/plugins/observability_solution/apm/public/hooks/use_current_user.ts

@@ -8,26 +8,26 @@
 import { useState, useEffect } from 'react';
 import { useKibana } from '@kbn/kibana-react-plugin/public';
 import { AuthenticatedUser } from '@kbn/security-plugin/common';
-import { ApmPluginStartDeps } from '../plugin';
+import { ApmServices } from '../plugin';
 
 export function useCurrentUser() {
   const {
-    services: { security },
-  } = useKibana<ApmPluginStartDeps>();
+    services: { securityService },
+  } = useKibana<ApmServices>();
 
   const [user, setUser] = useState<AuthenticatedUser>();
 
   useEffect(() => {
     const getCurrentUser = async () => {
       try {
-        const authenticatedUser = await security?.authc.getCurrentUser();
+        const authenticatedUser = await securityService.authc.getCurrentUser();
         setUser(authenticatedUser);
       } catch {
         setUser(undefined);
       }
     };
     getCurrentUser();
-  }, [security?.authc]);
+  }, [securityService.authc]);
 
   return user;
 }

x-pack/plugins/observability_solution/apm/public/plugin.ts

@@ -17,6 +17,7 @@ import {
   DEFAULT_APP_CATEGORIES,
   Plugin,
   PluginInitializerContext,
+  SecurityServiceStart,
 } from '@kbn/core/public';
 import type { DataPublicPluginSetup, DataPublicPluginStart } from '@kbn/data-plugin/public';
 import { DataViewsPublicPluginStart } from '@kbn/data-views-plugin/public';
@@ -107,6 +108,7 @@ export interface ApmPluginSetupDeps {
 }
 
 export interface ApmServices {
+  securityService: SecurityServiceStart;
   telemetry: ITelemetryClient;
 }
 
@@ -390,6 +392,7 @@ export class ApmPlugin implements Plugin<ApmPluginSetup, ApmPluginStart> {
           pluginsStart: pluginsStart as ApmPluginStartDeps,
           observabilityRuleTypeRegistry,
           apmServices: {
+            securityService: coreStart.security,
             telemetry,
           },
         });