[Dubbo] move the classes of model from config to rpc-api for reusing

[Jeff-Lv]

What is the purpose of the change

reusing those model in rpc module.

Brief changelog

the refactor is very safe with unit test convering.

[codecov-io]

Codecov Report

Merging #2636 into master will decrease coverage by 0.24%.
The diff coverage is 22.22%.

@@             Coverage Diff             @@
##             master   #2636      +/-   ##
===========================================
- Coverage     55.05%   54.8%   -0.25%     
+ Complexity     5283    5263      -20     
===========================================
  Files           571     571              
  Lines         25515   25510       -5     
  Branches       4532    4532              
===========================================
- Hits          14048   13982      -66     
- Misses         9352    9419      +67     
+ Partials       2115    2109       -6

Impacted Files	Coverage Δ	Complexity Δ
...rg/apache/dubbo/rpc/model/ProviderMethodModel.java	0% <ø> (ø)	0 <0> (?)
...a/org/apache/dubbo/rpc/model/ApplicationModel.java	0% <ø> (ø)	0 <0> (?)
...ava/org/apache/dubbo/qos/command/impl/Offline.java	95.83% <ø> (ø)	7 <0> (ø)	⬇️
...ain/java/org/apache/dubbo/qos/command/impl/Ls.java	85% <ø> (ø)	9 <0> (ø)	⬇️
...java/org/apache/dubbo/qos/command/impl/Online.java	83.33% <ø> (ø)	5 <0> (ø)	⬇️
...java/org/apache/dubbo/rpc/model/ProviderModel.java	0% <0%> (ø)	0 <0> (?)
...rg/apache/dubbo/rpc/model/ConsumerMethodModel.java	0% <0%> (ø)	0 <0> (?)
...java/org/apache/dubbo/rpc/model/ConsumerModel.java	0% <0%> (ø)	0 <0> (?)
.../java/org/apache/dubbo/config/ReferenceConfig.java	51.07% <100%> (+0.35%)	42 <0> (ø)	⬇️
...in/java/org/apache/dubbo/config/ServiceConfig.java	47.9% <100%> (-0.47%)	63 <0> (-1)
... and 12 more

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[chickenlj]

If it prevents reuse when staying in the config module, then let's move these classes to the rpc module.
This migration will have no effect on other functionalities but for telnet, please make sure telnet still works fine when doing this.