Unquarantine monitor tests

What does this MR do and why?

This MR contains a lot of changes. These are the key points:

• all_monitor_features_spec.rb and all_monitor_core_features_spec.rb have been consolidated in one test file. This is due to having many features now available in core and none ee specific.
• The test was reduced to minimal functionality (metrics creation and dashboard filtering) as the Monitor stage pivots and deprecates some of the previously covered functionality.
• The test no longer requires a Kubernetes cluster to scrap metrics from, simplifying it to a local setup of several containers illustrated below. This is just to ensure minimal validation on a Prometheus manual installation.
• Portions of test code were removed since views were no longer necessary to have selectors as tests do not cover such functionality.
• Images used in this setup can be found on https://gitlab.com/gitlab-org/quality/custom-images-gitlab-qa