feat(pageserver): drop disposable keys during gc-compaction

[skyzh]

Problem

close #9552, close #8920, part of #9114

Summary of changes

• Drop keys not belonging to this shard during gc-compaction to avoid constructing history that might have been truncated during shard compaction.
• Run gc-compaction at the end of shard compaction test.

[github-actions]

5525 tests run: 5298 passed, 1 failed, 226 skipped (full report)

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Failures on Postgres 17

• test_sharding_split_failures[failure20]: debug-x86-64

# Run all failed tests locally:
scripts/pytest -vv -n $(nproc) -k "test_sharding_split_failures[debug-pg17-failure20]"

Code coverage* (full report)

• functions: 31.5% (7930 of 25166 functions)
• lines: 49.6% (62842 of 126581 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
eba488a at 2024-11-18T19:37:36.702Z :recycle:}