[Security Solution] Restructure RM API integration tests directory

[nikitaindik]

Current Rule Management integration tests directory structure is a bit confusing.

There's a directory called rule_management that sits inside a directory called rules_management at x-pack/test/security_solution_api_integration/test_suites/detections_response/rules_management/rule_management

Perhaps, the inner "rule management" dir has a name that's too generic for a domain / feature, which may promote dumping all kinds of tests there. As an option, it might make more sense to move the tests contained in the inner "rules_management" dir to the domain level above, like

Or maybe we could group tests from this nested "rule management" directory somehow and move them one level above. Create a "rule_monitoring" directory, for example.

[elasticmachine]

Pinging @elastic/security-detection-rule-management (Team:Detection Rule Management)