Record process physical & virtual memory stats separately

[james-bebbington]

On Linux:

• Physical usage = Resident set size
• Virtual usage = Virtual memory size

On Windows:

• Physical usage = Working set size
• Virtual usage = Commit size (private virtual memory), aka. Page File Usage

From what I can tell, there is one difference in that Virtual Usage on Windows does not include shared virtual memory whereas on Linux it does, but I think these concepts are similar enough to use the same metric. WDYT @jrcamp?

[codecov]

Codecov Report

Merging #1403 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1403   +/-   ##
=======================================
  Coverage   90.67%   90.67%           
=======================================
  Files         221      221           
  Lines       15816    15825    +9     
=======================================
+ Hits        14341    14350    +9     
  Misses       1061     1061           
  Partials      414      414           

Impacted Files	Coverage Δ
...nternal/scraper/processscraper/process_metadata.go	100.00% <100.00%> (ø)
...internal/scraper/processscraper/process_scraper.go	98.38% <100.00%> (+0.01%)	⬆️

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[jrcamp]

@bogdandrutu please merge