FTR configurable test users for functional tests under Uptime app

[rashmivkulkarni]

Meta issue: #60815
App: Uptime

Objective :
We should run all CI tests with security enabled and with a user who has the minimal documented privileges to allow them to be successful.
Tests:

• x-pack/test/functional/apps/uptime/certificates.ts
• x-pack/test/functional/apps/uptime/locations.ts
• x-pack/test/functional/apps/uptime/ml_anomaly.ts
• x-pack/test/functional/apps/uptime/monitor.ts
• x-pack/test/functional/apps/uptime/overview.ts
• x-pack/test/functional/apps/uptime/ping_redirects.ts

Feature controls:

• x-pack/test/functional/apps/uptime/feature_controls/uptime_security.ts
• x-pack/test/functional/apps/uptime/feature_controls/uptime_spaces.ts

These feature control tests already using minimum required privileges to perform the test and also login and out through the UI, using the test_user service could optimize it.

cc @LeeDr

[elasticmachine]

Pinging @elastic/uptime (Team:uptime)