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]

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 61.49%. Comparing base (af6f3dc) to head (576861e).
Report is 4677 commits behind head on main.

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Additional details and impacted files

@@            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%)	⬇️

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[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?