[DUBBO-3137]: step4 - start to review RemotingConstants

[CrazyHZM]

What is the purpose of the change

issue #3137:
start to review RemotingConstants suitable to move back to its own module.

Brief changelog

XXXXX

Verifying this change

XXXXX

Follow this checklist to help us incorporate your contribution quickly and easily:

• Make sure there is a GITHUB_issue field for the change (usually before you start working on it). Trivial changes like typos do not require a GITHUB issue. Your pull request should address just this issue, without pulling in other changes - one PR resolves one issue.
• Format the pull request title like [Dubbo-XXX] Fix UnknownException when host config not exist #XXX. Each commit in the pull request should have a meaningful subject line and body.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Write necessary unit-test to verify your logic correction, more mock a little better when cross module dependency exist. If the new feature or significant change is committed, please remember to add sample in dubbo samples project.
• Run mvn clean install -DskipTests=false & mvn clean test-compile failsafe:integration-test to make sure unit-test and integration-test pass.
• If this contribution is large, please follow the Software Donation Guide.

[codecov-io]

Codecov Report

Merging #4057 into master will increase coverage by 0.6%.
The diff coverage is 50%.

@@             Coverage Diff             @@
##             master    #4057     +/-   ##
===========================================
+ Coverage     62.38%   62.99%   +0.6%     
  Complexity      544      544             
===========================================
  Files           777      756     -21     
  Lines         34412    32569   -1843     
  Branches       5403     5162    -241     
===========================================
- Hits          21468    20516    -952     
+ Misses        10475     9691    -784     
+ Partials       2469     2362    -107

Impacted Files	Coverage Δ	Complexity Δ
...ache/dubbo/common/constants/RemotingConstants.java	100% <ø> (ø)	0 <0> (ø)	⬇️
...emoting/transport/grizzly/GrizzlyCodecAdapter.java	0% <0%> (ø)	0 <0> (ø)	⬇️
...pache/dubbo/remoting/telnet/codec/TelnetCodec.java	50.61% <100%> (ø)	0 <0> (ø)	⬇️
...er/connection/ConnectionOrderedChannelHandler.java	69.04% <100%> (ø)	0 <0> (ø)	⬇️
...e/dubbo/remoting/http/tomcat/TomcatHttpServer.java	87.87% <100%> (ø)	0 <0> (ø)	⬇️
.../exchange/support/header/HeaderExchangeClient.java	86.76% <33.33%> (ø)	0 <0> (ø)	⬇️
...pache/dubbo/remoting/transport/AbstractServer.java	47.91% <33.33%> (ø)	0 <0> (ø)	⬇️
.../exchange/support/header/HeaderExchangeServer.java	67.92% <33.33%> (+0.94%)	0 <0> (ø)	⬇️
...bo/remoting/transport/netty/NettyCodecAdapter.java	53.12% <50%> (ø)	3 <0> (ø)	⬇️
...ubbo/remoting/transport/mina/MinaCodecAdapter.java	81.35% <50%> (ø)	3 <0> (ø)	⬇️
... and 25 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 0b380e3...7b0925e. Read the comment docs.

[beiwei30]

LGTM