[YUNIKORN-1107] Make health check occur in the background

[lowc1012]

What is this PR for?

• Change "ws/v1/scheduler/healthcheck" API to fetch health check cache in scheduler context
• Run health check periodically in the background

What type of PR is it?

• - Bug Fix
• - Improvement
• - Feature
• - Documentation
• - Hot Fix
• - Refactoring

Todos

• - Task

What is the Jira issue?

YUNIKORN-1107

How should this be tested?

Screenshots (if appropriate)

Questions:

• - The licenses files need update.
• - There is breaking changes for older versions.
• - It needs documentation.

[lowc1012]

@pbacsko Thanks for your review!
The above problems have been solved.

[HuangTing-Yao]

The codecov check doesn't triggered, also we can add TestHealthCheckerStartStop() for start() and stop() to make sure the panic won't happened.

[codecov]

Codecov Report

Merging #395 (acfdd01) into master (affcb27) will increase coverage by 0.06%.
The diff coverage is 70.83%.

@@            Coverage Diff             @@
##           master     #395      +/-   ##
==========================================
+ Coverage   69.54%   69.61%   +0.06%     
==========================================
  Files          67       67              
  Lines        9528     9592      +64     
==========================================
+ Hits         6626     6677      +51     
- Misses       2657     2670      +13     
  Partials      245      245              

Impacted Files	Coverage Δ
pkg/common/configs/config.go	76.66% <ø> (ø)
pkg/common/configs/configvalidator.go	86.97% <ø> (ø)
pkg/common/configs/configwatcher.go	85.71% <ø> (ø)
pkg/common/resources/resources.go	97.68% <ø> (ø)
pkg/common/security/acl.go	84.14% <ø> (ø)
pkg/common/security/usergroup.go	85.71% <ø> (ø)
pkg/common/server.go	0.00% <ø> (ø)
pkg/common/utils.go	71.01% <ø> (ø)
pkg/events/event_cache.go	93.18% <ø> (ø)
pkg/events/event_publisher.go	100.00% <ø> (ø)
... and 43 more

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[HuangTing-Yao]

LGTM