[3.0] Add connection pool

[EarthChen]

What is the purpose of the change

Brief changelog

Verifying this change

Checklist

• [x] 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.
• [ ] 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.
• [ ] Check if is necessary to patch to Dubbo 3 if you are work on Dubbo 2.7
• [ ] 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.
• [ ] Add some description to dubbo-website project if you are requesting to add a feature.
• [ ] GitHub Actions works fine on your own branch.
• [ ] If this contribution is large, please follow the Software Donation Guide.

[codecov-commenter]

Codecov Report

Merging #9950 (fbe577d) into 3.0 (7c72487) will decrease coverage by 0.19%. The diff coverage is 18.75%.

@@             Coverage Diff              @@
##                3.0    #9950      +/-   ##
============================================
- Coverage     65.70%   65.51%   -0.20%     
+ Complexity      319      318       -1     
============================================
  Files          1213     1240      +27     
  Lines         52949    53896     +947     
  Branches       8021     8127     +106     
============================================
+ Hits          34792    35310     +518     
- Misses        14367    14744     +377     
- Partials       3790     3842      +52     

Impacted Files	Coverage Δ
...java/org/apache/dubbo/remoting/api/Connection.java	70.00% <0.00%> (-1.32%)	:arrow_down:
.../org/apache/dubbo/remoting/api/ConnectionPool.java	0.00% <0.00%> (ø)
...ing/api/connection/DefaultConnectionPoolEntry.java	0.00% <0.00%> (ø)
...g/api/connection/DefaultConnectionPoolFactory.java	0.00% <0.00%> (ø)
...remoting/api/connection/DefaultConnectionPool.java	0.90% <0.90%> (ø)
...g/apache/dubbo/rpc/protocol/tri/TripleInvoker.java	56.32% <70.00%> (-0.17%)	:arrow_down:
...ting/api/connection/SingleConnectionPoolEntry.java	75.00% <75.00%> (ø)
.../remoting/api/connection/SingleConnectionPool.java	77.77% <77.77%> (ø)
...moting/api/MultiplexProtocolConnectionManager.java	100.00% <100.00%> (ø)
.../remoting/api/SingleProtocolConnectionManager.java	88.88% <100.00%> (+4.27%)	:arrow_up:
... and 224 more

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