[v24.3.x] archival: Rate-limit `segments_pending_deletion` metric recomputation

[vbotbuildovich]

Backport #25801 to branch v24.3.x. This issue was created as a placeholder because the original PR's commit(s) could not be automatically cherry-picked.
Here are the commands to execute:

git checkout v24.3.x
git checkout -b manual-backport-25801-v24.3.x-983
git cherry-pick -x 930996cd67 1e7925e035

git push origin manual-backport-25801-v24.3.x-983
gh pr create \
  --title "[v24.3.x] archival: Rate-limit `segments_pending_deletion` metric recomputation" \
  --base "v24.3.x" \
  --label "kind/backport" \
  --head "manual-backport-25801-v24.3.x-983" \
  --draft \
  --repo "redpanda-data/redpanda" \
  --milestone "v24.3.x-next" \
  --body "Backport of PR https://github.com/redpanda-data/redpanda/pull/25801 "

JIRA Link: [CORE-9808](https://redpandadata.atlassian.net/browse/CORE-9808)

[piyushredpanda]

@Lazin is this still needed for backport? cc: @lf-rep