[RAC] [Observability] Set up functional test service to provide preconfigured users

[weltenwort]

📓 Summary

Since several functional tests of the alerts page will need to use similar user/role/capabilities setups, we could pave the way for them by creating a functional test service that encapsulates the creation of users and role with common observability permission permutations.

✔️ Acceptance criteria

• A test service exist in x-pack/test/functional/services/observability that
  • provides a function to create and log in users with a role with given permissions suitable for use in a before hook
  • provides a function to log out and delete the created users and roles suitable for use in an after hook
  • provides predefined permission objects with all and read permissions for individual observability solutions separately
  • provides a predefined permission object all and read for all individual observability solutions at once
• The test observability service is registered in the overall functional test service mapping at https://github.com/elastic/kibana/blob/c510288c05089699a897e43c34b28c319ce9a472/x-pack/test/functional/services/index.ts

💡 Implementation hints

• Examples of user/role creation as well as login/logout can be found in

  kibana/x-pack/test/functional/apps/observability/feature_controls/observability_security.ts

  Lines 34 to 65 in c510288

  	before(async () => {
  	await security.role.create('cases_observability_all_role', {
  	elasticsearch: { cluster: [], indices: [], run_as: [] },
  	kibana: [
  	{ spaces: ['*'], base: [], feature: { observabilityCases: ['all'], logs: ['all'] } },
  	],
  	});
  	await security.user.create('cases_observability_all_user', {
  	password: 'cases_observability_all_user-password',
  	roles: ['cases_observability_all_role'],
  	full_name: 'test user',
  	});
  	await PageObjects.security.forceLogout();
  	await PageObjects.security.login(
  	'cases_observability_all_user',
  	'cases_observability_all_user-password',
  	{
  	expectSpaceSelector: false,
  	}
  	);
  	});
  	after(async () => {
  	await PageObjects.security.forceLogout();
  	await Promise.all([
  	security.role.delete('cases_observability_all_role'),
  	security.user.delete('cases_observability_all_user'),
  	]);
  	});

[elasticmachine]

Pinging @elastic/logs-metrics-ui (Team:logs-metrics-ui)