Improve logging for gc-compaction

[trungda]

Problem

• Inside compact_with_gc_inner, there is a similar log line:
  

  neon/pageserver/src/tenant/timeline/compaction.rs

  Lines 3181 to 3187 in db24ba9

  	info!(
  	"running enhanced gc bottom-most compaction, dry_run={dry_run}, compact_key_range={}..{}, compact_lsn_range={}..{}",
  	compact_key_range.start,
  	compact_key_range.end,
  	compact_lsn_range.start,
  	compact_lsn_range.end
  	);

• Also, I think it would be useful when debugging to have the ability to select a particular sub-compaction job (e.g., 1/100) to see all the logs for that job.

Summary of changes

• Attach a span to the compact_with_gc_inner.

CC: @skyzh

[github-actions]

8481 tests run: 7899 passed, 0 failed, 582 skipped (full report)

---

Flaky tests (1)

Postgres 17

• test_sharding_split_failures[failure2]: debug-x86-64-without-lfc

Code coverage* (full report)

• functions: 32.1% (9024 of 28101 functions)
• lines: 48.4% (80211 of 165716 lines)

* collected from Rust tests only

---

_{The comment gets automatically updated with the latest test results
7aba940 at 2025-06-13T04:22:50.876Z :recycle:}

[skyzh]

link to the related issue #11528, thank you for the help on this :)

[trungda]

Oh nice! Didn't know there was an issue on this. Let me know if we can help with the original ticket. Also, let me know your thought on this: #12278. We are happy to help (and get help) in this area.