[yurthub] enhancements and fixes for function cancellation

[zhaodiaoer]

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 bug
/kind enhancement

What this PR does / why we need it:

• remove a bunch of unused stopCh variable in functions
• stop bind lifecycle variable(stopCh) to manager type struct
• prefer use context to control long-runing functions' cacellation
• fix some never closed stopCh
• align the context of test target to testing.T in test code

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

NONE

other Note

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
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

[codecov]

Codecov Report

Attention: Patch coverage is 43.75000% with 45 lines in your changes missing coverage. Please review.

Please upload report for BASE (master@2b7106e). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
cmd/yurthub/app/start.go	0.00%	12 Missing ⚠️
pkg/yurthub/server/server.go	0.00%	6 Missing ⚠️
pkg/yurthub/tenant/tenant.go	0.00%	4 Missing ⚠️
pkg/yurthub/multiplexer/filterstore.go	0.00%	3 Missing ⚠️
pkg/yurthub/proxy/proxy.go	0.00%	3 Missing ⚠️
pkg/yurthub/proxy/remote/loadbalancer.go	40.00%	3 Missing ⚠️
pkg/yurthub/filter/objectfilter/chain.go	0.00%	2 Missing ⚠️
pkg/yurthub/gc/gc.go	0.00%	2 Missing ⚠️
pkg/yurthub/network/network.go	0.00%	2 Missing ⚠️
pkg/yurthub/proxy/local/local.go	0.00%	2 Missing ⚠️
... and 4 more

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #2411   +/-   ##
=========================================
  Coverage          ?   42.05%           
=========================================
  Files             ?      395           
  Lines             ?    25956           
  Branches          ?        0           
=========================================
  Hits              ?    10915           
  Misses            ?    14021           
  Partials          ?     1020           

Flag	Coverage Δ
unittests	42.05% <43.75%> (?)

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