chore: Renames "realm" occurrences to App Services

[maastha]

Proposed changes

Renames "realm" occurrences to App Services. Cleaning up wherever required.

Jira ticket: CLOUDP-273338

Please include a summary of the fix/feature/change, including any relevant motivation and context.

Link to any related issue(s):

Type of change:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as
  expected)
• This change requires a documentation update
• If changes include removal or addition of 3rd party GitHub actions, I updated our internal document. Reach out to the APIx Integration slack channel to get access to the internal document.

Manual QA performed:

• cfn invoke for each of CRUDL/cfn test
• Updated resource in example
• Published to AWS private registry
• Used the template in example to create and update a stack in AWS
• Deleted stack to ensure resources are deleted
• Created multiple resources in same stack
• Validated in Atlas UI
• Included screenshots

Required Checklist:

• I have signed the MongoDB CLA
• I have added tests that prove my fix is effective or that my feature works
• I have checked that this change does not generate any credentials and that they are NOT accidentally logged anywhere.
• I have added any necessary documentation (if appropriate)
• I have run make fmt and formatted my code
• For CFN Resources: I have released by changes in the private registry and proved by change
  works in Atlas

Further comments

[maastha]

making consistent with other test files

[lantoli]

can tests work without ServiceId and FunctionId?

[maastha]

They can't but the test script does replace these values with the set env vars (similar to other tests). Removing these from the JSON because I found these placeholders confusing