should not use IdentityHashMap, otherwise cannot use method object to get

[beiwei30]

What is the purpose of the change

switch from IdentityHashMap to HashMap

Brief changelog

XXXXX

Verifying this change

XXXXX

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[codecov-io]

Codecov Report

Merging #5675 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master    #5675      +/-   ##
============================================
- Coverage     61.13%   61.13%   -0.01%     
+ Complexity      422      421       -1     
============================================
  Files           923      923              
  Lines         37568    37568              
  Branches       5441     5441              
============================================
- Hits          22969    22967       -2     
- Misses        12103    12105       +2     
  Partials       2496     2496

Impacted Files	Coverage Δ	Complexity Δ
...java/org/apache/dubbo/rpc/model/ConsumerModel.java	58.13% <100%> (ø)	0 <0> (ø)	⬇️
...ng/exchange/support/header/HeartbeatTimerTask.java	73.68% <0%> (-5.27%)	0% <0%> (ø)
...e/dubbo/remoting/transport/netty/NettyChannel.java	52.27% <0%> (-3.41%)	19% <0%> (-1%)
...bo/rpc/cluster/support/FailbackClusterInvoker.java	67.21% <0%> (-3.28%)	0% <0%> (ø)
...pache/dubbo/registry/support/AbstractRegistry.java	77.15% <0%> (-3%)	0% <0%> (ø)
...ache/dubbo/remoting/transport/mina/MinaClient.java	56.92% <0%> (-1.54%)	8% <0%> (-1%)
.../dubbo/remoting/transport/netty4/NettyChannel.java	65.34% <0%> (-1%)	0% <0%> (ø)
...rg/apache/dubbo/common/timer/HashedWheelTimer.java	63.1% <0%> (+0.68%)	0% <0%> (ø)	⬇️
...a/org/apache/dubbo/monitor/dubbo/DubboMonitor.java	88.57% <0%> (+1.9%)	16% <0%> (ø)	⬇️
...he/dubbo/remoting/transport/netty/NettyServer.java	73.68% <0%> (+3.5%)	9% <0%> (+1%)	⬆️
... and 3 more

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[qinliujie]

LGTM