feat: improve direct clientsets for 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 enhancement

What this PR does / why we need it:

Use Clientset directly instead of using rest config in order to improve the performance of yurthub. because yurthub.conf file should be loaded when rest config is used each time.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

other Note

[rambohe-ch]

@zyjhtangtang @vie-serendipity PTAL

[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

[rambohe-ch]

@zyjhtangtang @vie-serendipity PTAL

[codecov]

Codecov Report

Attention: Patch coverage is 54.28571% with 32 lines in your changes missing coverage. Please review.

Project coverage is 46.40%. Comparing base (175c309) to head (7b661fe).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/yurthub/gc/gc.go	0.00%	8 Missing ⚠️
pkg/yurthub/proxy/autonomy/autonomy.go	42.85%	8 Missing ⚠️
cmd/yurthub/app/start.go	0.00%	5 Missing ⚠️
pkg/yurthub/kubernetes/directclient/manager.go	85.71%	2 Missing and 2 partials ⚠️
pkg/yurthub/server/server.go	0.00%	4 Missing ⚠️
pkg/yurthub/server/nonresource.go	60.00%	2 Missing ⚠️
pkg/yurthub/proxy/proxy.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2285      +/-   ##
==========================================
+ Coverage   46.20%   46.40%   +0.20%     
==========================================
  Files         416      416              
  Lines       27279    27266      -13     
==========================================
+ Hits        12604    12653      +49     
+ Misses      13404    13333      -71     
- Partials     1271     1280       +9     

Flag	Coverage Δ
unittests	46.40% <54.28%> (+0.20%)	⬆️

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[zyjhtangtang]

/LGTM

[rambohe-ch]

/backport release-v1.6

[github-actions]

Successfully created backport PR for release-v1.6:

• [Backport release-v1.6] feat: improve direct clientsets for yurthub #2290