fix(ecstore): route rebalance delete markers to store and count expiries
Rebalance migrated delete markers via SetDisks::delete_object (single set,
no cross-pool routing), which silently rewrote the marker back onto the
source set. The subsequent source cleanup then deleted the whole entry,
losing the delete marker and reviving logically-deleted objects (#942, P0).
Route delete-marker migration through ECStore::delete_object via a store-
level closure that mirrors the existing transfer closure, so the marker
lands on the cross-pool target honouring data_movement/src_pool_idx/
delete_marker; on failure it is not counted as moved, so the source entry
is not cleaned up. The unused MigrationBackend::delete_object_for_migration
footgun is removed.
Rebalance source cleanup also ignored lifecycle-expired versions: the gate
used rebalanced == total_versions and passed an empty allowed_missing, so
any entry with an expired version could never be cleaned up, leaking the
migrated versions in the source pool (#950). Mirror decommission: gate on
rebalanced + expired == total_versions and feed expired version identities
into the cleanup preflight allowed_missing, plus a source_retained warning
for parity with decommission diagnostics.
Adds regression tests for delete-marker store routing and the expiry-aware
cleanup gate.
Co-authored-by: heihutu <heihutu@gmail.com>
cxymds