cls/fifo: Remove all use of part tags

cls/fifo: Remove all use of part tags

Part tags make part creation and setting the head non-idempotent,
leading to issues where racing RGWs may get confused about the correct
tag for a part. (Or worse, potentially have the metadata header hold
different value for a part than the part's header.)

Consistently only requires that all nodes agree on the number.

Fixes: https://tracker.ceph.com/issues/57562
Signed-off-by: Adam C. Emerson <aemerson@redhat.com>
(cherry picked from commit f89a6d1833f45220ce558919de656f99cd1c9342)
Conflicts:
	src/neorados/cls/fifo.cc
	src/neorados/cls/fifo.h
	src/test/cls_fifo/bench_cls_fifo.cc
	src/test/cls_fifo/test_cls_fifo.cc
 - Upstream deleted version has changes not in downstream
	src/cls/fifo/cls_fifo_ops.h
 - Upstream std::
	src/cls/fifo/cls_fifo_types.h
 - Upstream friend operator
 - Upstream std::
	src/rgw/CMakeLists.txt
 - Downstream unneeded library dependency
	src/rgw/cls_fifo_legacy.h
 - Upstream dpp
	src/rgw/cls_fifo_legacy.cc
 - Upstream C++20
 - Upstream dpp

Fixes: https://tracker.ceph.com/issues/58403
Signed-off-by: Adam C. Emerson <aemerson@redhat.com>