Added cpu load scraper

[james-bebbington]

Link to tracking Issue:
#847

Description:
Added load scraper to the hostmetricsreceiver which:

• On Unix-based systems, uses gopsutil to collect load metrics
• On Windows, samples the "Processor Queue Length" performance counter over 5s intervals and computes similar load averages (similar to what psutil does)

Metrics:

[bogdandrutu]

Please rebase, all imports changed :)

[codecov-commenter]

Codecov Report

Merging #974 into master will increase coverage by 0.06%.
The diff coverage is 96.72%.

@@            Coverage Diff             @@
##           master     #974      +/-   ##
==========================================
+ Coverage   85.62%   85.69%   +0.06%     
==========================================
  Files         184      188       +4     
  Lines       13087    13148      +61     
==========================================
+ Hits        11206    11267      +61     
+ Misses       1434     1433       -1     
- Partials      447      448       +1     

Impacted Files	Coverage Δ
...eiver/internal/scraper/loadscraper/load_scraper.go	92.00% <92.00%> (ø)
receiver/hostmetricsreceiver/factory.go	73.07% <100.00%> (+0.52%)	⬆️
...csreceiver/internal/scraper/loadscraper/factory.go	100.00% <100.00%> (ø)
...ver/internal/scraper/loadscraper/load_constants.go	100.00% <100.00%> (ø)
...nternal/scraper/loadscraper/load_scraper_others.go	100.00% <100.00%> (ø)
translator/internaldata/resource_to_oc.go	76.47% <0.00%> (ø)
... and 1 more

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