storage: fix inability to update liveness in mixed version clusters

The encoding of `storage.Liveness` changed in cockroachdb#18910 which caused node
liveness updates to fail in mixed version clusters due to failed
conditional puts. Because the encoding changed, continued attempts to
update the liveness would never succeed. Changed `Liveness.expiration`
to use the `LegacyTimestamp` type.

Audited the code and the only protos that are used as the expected value
in conditional put operations are `storage.Liveness` and
`roachpb.RangeDescriptor`. Extended TestBelowRaftProtos to verify the
encoding of these protos does not change unexpectedly.

Consistency checks were failing in mixed version clusters because of an
explicit call to marshal an `hlc.Timestamp` in `Replica.sha512`.

Fixes cockroachdb#18940

build/protobuf.mk

@@ -58,7 +58,7 @@ UI_JS := $(UI_ROOT)/src/js/protos.js
 UI_TS := $(UI_ROOT)/src/js/protos.d.ts
 UI_SOURCES := $(UI_JS) $(UI_TS)
 
-CPP_PROTOS := $(filter %/roachpb/metadata.proto %/roachpb/data.proto %/roachpb/internal.proto %/engine/enginepb/mvcc.proto %/engine/enginepb/rocksdb.proto %/hlc/timestamp.proto %/unresolved_addr.proto,$(GO_PROTOS))
+CPP_PROTOS := $(filter %/roachpb/metadata.proto %/roachpb/data.proto %/roachpb/internal.proto %/engine/enginepb/mvcc.proto %/engine/enginepb/rocksdb.proto %/hlc/legacy_timestamp.proto %/hlc/timestamp.proto %/unresolved_addr.proto,$(GO_PROTOS))
 CPP_HEADERS := $(subst ./,$(NATIVE_ROOT)/,$(CPP_PROTOS:%.proto=%.pb.h))
 CPP_SOURCES := $(subst ./,$(NATIVE_ROOT)/,$(CPP_PROTOS:%.proto=%.pb.cc))
 

c-deps/libroach/CMakeLists.txt

@@ -29,6 +29,7 @@ add_library(roach
   protos/cockroach/pkg/roachpb/metadata.pb.cc
   protos/cockroach/pkg/storage/engine/enginepb/mvcc.pb.cc
   protos/cockroach/pkg/storage/engine/enginepb/rocksdb.pb.cc
+  protos/cockroach/pkg/util/hlc/legacy_timestamp.pb.cc
   protos/cockroach/pkg/util/hlc/timestamp.pb.cc
   protos/cockroach/pkg/util/unresolved_addr.pb.cc
 )