[release-15.0] OnlineDDL: cleanup cancelled migration artifacts; support `--retain-artifacts=<duration>` DDL strategy flag (#14029)#14035

Merged

shlomi-noach merged 2 commits intorelease-15.0from backport-14029-to-release-15.0

Sep 20, 2023

+122-6

Commits on Sep 19, 2023

Cherry-pick 0461faf with conflicts
vitess-bot[bot]
committed

Commits on Sep 20, 2023

resolved conflict
shlomi-noach
committed