[v24.2.x] [CORE-627] archival: Convert assertion to exception

[vbotbuildovich]

Backport #24580 to branch v24.2.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 v24.2.x
git checkout -b manual-backport-24580-v24.2.x-855
git cherry-pick -x 0648eb0c6d f1253b2cb5

git push origin manual-backport-24580-v24.2.x-855
gh pr create \
  --title "[v24.2.x] [CORE-627] archival: Convert assertion to exception" \
  --base "v24.2.x" \
  --label "kind/backport" \
  --head "manual-backport-24580-v24.2.x-855" \
  --draft \
  --repo "redpanda-data/redpanda" \
  --milestone "v24.2.x-next" \
  --body "Backport of PR https://github.com/redpanda-data/redpanda/pull/24580 "

JIRA Link: [CORE-8667](https://redpandadata.atlassian.net/browse/CORE-8667)