[ISSUE #4850] fix apollo as registry, client metadata and uri cannot be synchronized to admin

[xuziyang]

1. unified client registration metadata and admin read metadata key
2. unified the data format of admin and client
3. when admin starts, perform a read operation from apollo
4. The registration of metadata is optimized. When the meta data does not change, the metadata write operation is not performed
5. removed useless code

[codecov-commenter]

Codecov Report

Merging #4851 (c8f49e1) into master (21f4dba) will increase coverage by 0.04%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #4851      +/-   ##
============================================
+ Coverage     64.57%   64.61%   +0.04%     
- Complexity     8201     8202       +1     
============================================
  Files          1153     1153              
  Lines         34019    34019              
  Branches       3047     3047              
============================================
+ Hits          21967    21981      +14     
+ Misses        10314    10298      -16     
- Partials       1738     1740       +2     

see 3 files with indirect coverage changes

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