embed: unlimit the recv msg size of grpc-gateway

[spacewander]

Ensure the client which access etcd via grpc-gateway won't
be limited by the MaxCallRecvMsgSize. Here we choose the same
default value of etcdcli as grpc-gateway's MaxCallRecvMsgSize.

Fix #12576

[spacewander]

I am not familiar with etcd's test so I don't know how to test it in the CI.
I test it locally and it works well.

[codecov-commenter]

Codecov Report

Merging #13077 (576861e) into main (af6f3dc) will decrease coverage by 6.40%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main   #13077      +/-   ##
==========================================
- Coverage   67.90%   61.49%   -6.41%     
==========================================
  Files         437      418      -19     
  Lines       33831    33009     -822     
==========================================
- Hits        22973    20299    -2674     
- Misses       8895    10637    +1742     
- Partials     1963     2073     +110     

Flag	Coverage Δ
all	61.49% <100.00%> (-6.41%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
server/embed/serve.go	64.14% <100.00%> (+0.55%)	⬆️
raft/quorum/quorum.go	0.00% <0.00%> (-100.00%)	⬇️
raft/tracker/state.go	0.00% <0.00%> (-100.00%)	⬇️
server/mvcc/backend/hooks.go	0.00% <0.00%> (-100.00%)	⬇️
server/etcdserver/api/v2v3/watcher.go	0.00% <0.00%> (-82.09%)	⬇️
client/pkg/v3/testutil/recorder.go	0.00% <0.00%> (-79.67%)	⬇️
pkg/flags/unique_urls.go	0.00% <0.00%> (-76.93%)	⬇️
server/etcdserver/api/v3compactor/revision.go	0.00% <0.00%> (-76.93%)	⬇️
pkg/flags/unique_strings.go	0.00% <0.00%> (-75.00%)	⬇️
client/pkg/v3/transport/listener_opts.go	13.33% <0.00%> (-73.34%)	⬇️
... and 201 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update af6f3dc...576861e. Read the comment docs.

[spacewander]

Ping @ptabor @gyuho

[membphis]

Very useful PR, looking forward to being merged soon

[tangcong]

lgtm.
The etcd gRPC Server MaxSendMsgSize is also math.MaxInt32. @gyuho PTAL.

[gyuho]

@spacewander @tangcong Sorry for the delay. Can we also backport to 3.5?

[tangcong]

#13099 #13100 done. APISIX and other projects are currently mainly using etcd 3.4, and it is better that we can also backport it to 3.4. thanks @gyuho

[wayne-cheng]

@tangcong There are still many users using the version 3.3，could you also backport it to 3.3?