Draft: [RUN ALL RSPEC] Automatically create gitlab_ci schema on db:test:prepare

What does this MR do?

Automatically create gitlab_ci schema on db:test:prepare.

We enhance db:test:prepare to automatically create gitlab_ci schema, and move certain tables to that schema. This only happens in test environment. This can be disabled, which is especially useful while we transition GDK to have the right search path.

For convenience/testing there is a rake task to do the same in development environment.

Warns if your schema search path does not contain gitlab_ci.

More tables will be migrated as part of &6451 (closed) epic

Related issue: #337813 (closed)

Screenshots or Screencasts (strongly suggested)

How to setup and validate locally (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are 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.
• This change is backwards compatible across updates, or this does not apply.

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.)