Rename Service model to Integration [RUN ALL RSPEC] [RUN AS-IF-FOSS]

What does this MR do?

This MR renames the Service model to Integration.

See:

• #201848 (closed)
• &2504 (closed)

Reviewing tip

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Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have not included a changelog entry because non-client-facing change.
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Related to #201848 (closed)