feat: remove yurt-coordinator from yurthub

[rambohe-ch]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespace from that line:
/kind bug
/kind documentation
/kind enhancement
/kind good-first-issue
/kind feature
/kind question
/kind design
/sig ai
/sig iot
/sig network
/sig storage

/kind feature

What this PR does / why we need it:

remove the code related to yurt-coordinator in Yurthub component.

Which issue(s) this PR fixes:

Fixes #2257

Special notes for your reviewer:

Does this PR introduce a user-facing change?

other Note

[rambohe-ch]

@YTGhost PTAL

[codecov]

Codecov Report

Attention: Patch coverage is 38.23529% with 21 lines in your changes missing coverage. Please review.

Project coverage is 46.10%. Comparing base (a382ab9) to head (59e16d0).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/yurthub/proxy/proxy.go	0.00%	16 Missing ⚠️
pkg/yurthub/proxy/remote/loadbalancer.go	0.00%	4 Missing ⚠️
cmd/yurthub/app/start.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2276      +/-   ##
==========================================
+ Coverage   45.36%   46.10%   +0.73%     
==========================================
  Files         427      415      -12     
  Lines       29105    27186    -1919     
==========================================
- Hits        13204    12533     -671     
+ Misses      14586    13383    -1203     
+ Partials     1315     1270      -45     

Flag	Coverage Δ
unittests	46.10% <38.23%> (+0.73%)	⬆️

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[YTGhost]

LGTM