Follow up refactoring for group-level protected environments [RUN ALL RSPEC] [RUN AS-IF-FOSS]

NOTE: This is a blocker against the critical issue for important prospects, thus the priority is relatively high

What does this MR do?

We're currently working onto shipping Group-level permissions config for Protected Environments. Previously, we refactored the project-level protected environments as a preparation, but still the change size of the feature implementation MR is pretty big. Therefore, we're following up to the refactoring to reduce the change size in order to ease the review pains.

Specifically, this MR introduces the following changes:

• Use Ci::Build#persisted_environment instead of instantized_environment.
• Handle N+1 issue related to persisted_environment with BatchLoader. This is already in place.
• Inherit BaseContainerService in Protected Environment services for supporting both project and group container types.

Please note that there are no behavioral changes on the existing features.

Related #215888 (closed)

Does this MR meet the acceptance criteria?

Conformity

• I have included a changelog entry, or it's not needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.