Allow a job token to identify himself on /job

What does this MR do?

Allow a CI job token to retrieve self job using that token.

For example the endpoint /user exists for access token only, add the same endpoint on /job but for job token only

Partially solve #24123 (closed).

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

What additional test coverage or changes to tests will be needed? added same tests than other user and job Will it require cross-browser testing? no because it's an api update only

• 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