storcon: add API definitions for exclude_timeline and term_bump

[arpad-m]

Adds API definitions for the safekeeper API endpoints exclude_timeline and term_bump. Also does a bugfix to return the correct type from delete_timeline.

Part of #8614

[github-actions]

7909 tests run: 7525 passed, 0 failed, 384 skipped (full report)

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Code coverage* (full report)

• functions: 32.5% (8727 of 26885 functions)
• lines: 48.5% (74653 of 154040 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
5445d24 at 2025-03-12T18:07:46.562Z :recycle:}