refactor(sysadvisor): emit metrics even when reclaim disabled

[cheney-lin]

What type of PR is this?

Enhancements

What this PR does / why we need it:

Which issue(s) this PR fixes:

Special notes for your reviewer:

[codecov]

Codecov Report

Patch coverage: 91.66% and project coverage change: -0.01 ⚠️

Comparison is base (f3ce63d) 50.92% compared to head (a5e77fc) 50.91%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #38      +/-   ##
==========================================
- Coverage   50.92%   50.91%   -0.01%     
==========================================
  Files         311      311              
  Lines       31785    31790       +5     
==========================================
+ Hits        16185    16187       +2     
- Misses      13682    13684       +2     
- Partials     1918     1919       +1     

Flag	Coverage Δ
unittest	50.91% <91.66%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...r/plugin/qosaware/reporter/manager/resource/cpu.go	100.00% <ø> (ø)
...lugin/qosaware/reporter/manager/resource/memory.go	100.00% <ø> (ø)
.../sysadvisor/qosaware/reporter/headroom_reporter.go	100.00% <ø> (ø)
.../sysadvisor/qosaware/reporter/headroom_reporter.go	70.83% <66.66%> (ø)
...ugin/qosaware/reporter/manager/resource/generic.go	100.00% <100.00%> (ø)

... and 7 files with indirect coverage changes

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[waynepeking348]

why we still need to emit reclaimed resources when reclaim is disabled?

[cheney-lin]

Make the metrics continuous. Image that if the metrics between time1 to time2 is missed, the front-end grafana will connect the two point directly, giving the impression that the headrooms in this time span is non-zero.