test(s3/lifecycle): pin toProtoActionKind + toProtoIdentity
The two converters are the worker-side wire to LifecycleDelete; a
miss in toProtoActionKind sends ACTION_KIND_UNSPECIFIED that the
server rejects FATAL, and a wrong toProtoIdentity flips the CAS
witness so every dispatch comes back NOOP_RESOLVED with STALE_IDENTITY
even though the entry hasn't changed.
10 tests pin: every listed s3lifecycle.ActionKind maps to its proto
counterpart (table-driven, one subtest per kind); ActionKindUnspecified
and a future unknown kind both collapse to ACTION_KIND_UNSPECIFIED
(forward compat); nil EntryIdentity stays nil (preserves the no-CAS
sentinel); a populated identity copies every field; a zero-valued
identity still produces a non-nil output so the server treats it as
a real CAS witness rather than no-CAS.