[DUBBO-3137]: move MetadataReportConstants back into metata-report-api module

[beiwei30]

What is the purpose of the change

issue #3137 : move MetadataReportConstants back into metata-report-api module

Brief changelog

XXXXX

Verifying this change

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[ralf0131]

Could you please hold this until #4025 is merged?

[CrazyHZM]

LGTM

[codecov-io]

Codecov Report

Merging #4049 into master will increase coverage by 0.01%.
The diff coverage is 42.85%.

@@             Coverage Diff              @@
##             master    #4049      +/-   ##
============================================
+ Coverage     63.12%   63.14%   +0.01%     
- Complexity      565      566       +1     
============================================
  Files           753      753              
  Lines         32417    32414       -3     
  Branches       5145     5145              
============================================
+ Hits          20464    20467       +3     
+ Misses         9598     9593       -5     
+ Partials       2355     2354       -1

Impacted Files	Coverage Δ	Complexity Δ
...a/org/apache/dubbo/metadata/support/Constants.java	100% <ø> (ø)	0 <0> (?)
...c/main/java/org/apache/dubbo/common/Constants.java	0% <ø> (-75%)	0 <0> (ø)
...bo/metadata/integration/MetadataReportService.java	78.04% <0%> (ø)	0 <0> (ø)	⬇️
...dubbo/metadata/support/AbstractMetadataReport.java	71.09% <75%> (ø)	0 <0> (ø)	⬇️
.../exchange/support/header/HeaderExchangeServer.java	66.98% <0%> (-0.95%)	0% <0%> (ø)
...g/apache/dubbo/registry/consul/ConsulRegistry.java	59.6% <0%> (-0.67%)	27% <0%> (ø)
...he/dubbo/registry/multicast/MulticastRegistry.java	69.23% <0%> (-0.46%)	0% <0%> (ø)
...dubbo/rpc/protocol/dubbo/CallbackServiceCodec.java	80.88% <0%> (+0.73%)	0% <0%> (ø)	⬇️
...pache/dubbo/remoting/transport/AbstractServer.java	48.95% <0%> (+1.04%)	0% <0%> (ø)	⬇️
...che/dubbo/remoting/transport/mina/MinaChannel.java	55.26% <0%> (+1.31%)	18% <0%> (+1%)	⬆️
... and 3 more

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