<tcp-proxy> admin background interface

[Redick01]

about #4534 complete admin background interface

Make sure that:

• [ x] You have read the contribution guidelines.
• [ x] You submit test cases (unit or integration tests) that back your changes.
• [ x] Your local test passed ./mvnw clean install -Dmaven.javadoc.skip=true.

[codecov-commenter]

Codecov Report

Merging #4766 (70ed433) into master (490ee7a) will decrease coverage by 0.75%.
The diff coverage is 13.03%.

@@             Coverage Diff              @@
##             master    #4766      +/-   ##
============================================
- Coverage     66.36%   65.61%   -0.75%     
- Complexity     8110     8114       +4     
============================================
  Files          1122     1130       +8     
  Lines         32572    32965     +393     
  Branches       2936     2960      +24     
============================================
+ Hits          21615    21629      +14     
- Misses         9240     9615     +375     
- Partials       1717     1721       +4     

Impacted Files	Coverage Δ
...enyu/admin/controller/ProxySelectorController.java	30.00% <0.00%> (ø)
...nyu/admin/discovery/DefaultDiscoveryProcessor.java	18.60% <0.00%> (ø)
...rg/apache/shenyu/admin/model/dto/DiscoveryDTO.java	0.00% <0.00%> (ø)
...pache/shenyu/admin/model/dto/ProxySelectorDTO.java	0.00% <ø> (-89.48%)	⬇️
.../apache/shenyu/admin/model/entity/DiscoveryDO.java	0.00% <0.00%> (ø)
.../shenyu/admin/model/entity/DiscoveryHandlerDO.java	0.00% <0.00%> (ø)
...ache/shenyu/admin/model/entity/DiscoveryRelDO.java	0.00% <0.00%> (ø)
...shenyu/admin/model/entity/DiscoveryUpstreamDO.java	81.08% <ø> (ø)
...he/shenyu/admin/model/enums/DiscoveryTypeEnum.java	0.00% <0.00%> (ø)
.../org/apache/shenyu/admin/model/vo/DiscoveryVO.java	0.00% <0.00%> (ø)
... and 11 more

... and 2 files with indirect coverage changes

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[Redick01]

complete admin background interface