[Dubbo-3875] dubbo TagRouter does not work with dubbo:parameter.

[chickenlj]

What is the purpose of the change

Fixes #3875, support using the following on consumer side:
<dubbo:parameter key="dubbo.tag" value="groupA"/>

Related issue #3359

Brief changelog

XXXXX

Verifying this change

XXXXX

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[chickenlj]

I think we should add 'tag' as the first class supporting item in XML on consumer side.

[codecov-io]

Codecov Report

Merging #3883 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##             master   #3883      +/-   ##
===========================================
- Coverage     63.71%   63.7%   -0.01%     
  Complexity       71      71              
===========================================
  Files           712     712              
  Lines         31443   31435       -8     
  Branches       5072    5069       -3     
===========================================
- Hits          20033   20026       -7     
- Misses         9113    9115       +2     
+ Partials       2297    2294       -3

Impacted Files	Coverage Δ	Complexity Δ
...org/apache/dubbo/config/AbstractServiceConfig.java	100% <ø> (ø)	0 <0> (ø)	⬇️
.../dubbo/config/builders/AbstractServiceBuilder.java	97.53% <ø> (-0.12%)	0 <0> (ø)
...ubbo/config/builders/AbstractInterfaceBuilder.java	98.05% <100%> (+0.07%)	0 <0> (ø)	⬇️
.../java/org/apache/dubbo/config/ReferenceConfig.java	60.51% <100%> (-0.72%)	0 <0> (ø)
...apache/dubbo/rpc/cluster/support/ClusterUtils.java	76.27% <100%> (+5.3%)	0 <0> (ø)	⬇️
...in/java/org/apache/dubbo/config/ServiceConfig.java	56.58% <100%> (ø)	0 <0> (ø)	⬇️
...g/apache/dubbo/config/AbstractInterfaceConfig.java	72.41% <100%> (+0.23%)	0 <0> (ø)	⬇️
...ache/dubbo/remoting/p2p/support/AbstractGroup.java	45.45% <0%> (-11.37%)	0% <0%> (ø)
.../apache/dubbo/remoting/transport/AbstractPeer.java	58.69% <0%> (-4.35%)	0% <0%> (ø)
...bo/rpc/cluster/support/FailbackClusterInvoker.java	67.21% <0%> (-3.28%)	0% <0%> (ø)
... and 5 more

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[ralf0131]

LGTM