Continue PR #221 while retaining its original commits and authorship.
Route latest-only fallback reads through the namespace lock used by normal
writes, propagate terminal scan errors before cache completion, and retain
delete markers until the cross-pool merge has resolved them.
Recount narrowly eligible latest null-version metadata when mixed erasure
layouts prevent selection. Keep each EC group separate and preserve the
requested quorum, strict resolution, and version-listing behavior.
Add regression coverage for locking, terminal errors, cache completion,
delete markers, mixed EC layouts, and HTTP behavior; run focused race tests
in CI. Verified with make test, focused race tests, and local distributed
single- and multi-pool rolling-restart workloads with exact final oracles.
Refs: https://github.com/pgsty/silo/issues/218
Refs: https://github.com/pgsty/silo/pull/221
Signed-off-by: Feng Ruohang <rh@vonng.com>
Feng Ruohang