[WIP]:sparkles: config agent leader election by klusterletconfig

[haoqing0110]

Summary

Previously submitted PR #695 to enable leader election of klusterlet-agent on single node managed cluster. It breaks some user e2e testing cases as they are using SNO for testing #708, enabling the SNO leader election might cause the agent to wait as bad as 137s to start working.

Create this PR to make the agent leader election time configurable by klusterletconfig, so that user can reduce the time in testing.

Related issue(s)

#695
#708

[openshift-ci]

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[haoqing0110]

/hold more testing cases to add.

[codecov]

Codecov Report

Attention: Patch coverage is 83.33333% with 12 lines in your changes missing coverage. Please review.

Project coverage is 63.57%. Comparing base (93db6de) to head (247308d).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...lers/klusterletcontroller/klusterlet_controller.go	92.18%	4 Missing and 1 partial ⚠️
pkg/singleton/spoke/agent.go	0.00%	4 Missing ⚠️
pkg/registration/spoke/spokeagent.go	25.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #719      +/-   ##
==========================================
+ Coverage   63.48%   63.57%   +0.09%     
==========================================
  Files         185      185              
  Lines       17827    17883      +56     
==========================================
+ Hits        11317    11369      +52     
- Misses       5578     5581       +3     
- Partials      932      933       +1     

Flag	Coverage Δ
unit	63.57% <83.33%> (+0.09%)	⬆️

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[openshift-merge-robot]

PR needs rebase.

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