Change host metrics receiver to use the new metrics internal structs

[bogdandrutu]

The most important changes are in the metadata files, others are just simple renaming.

Updates #1657

Depends on #1684 which adds the SetDataType and adds tests for it.

[codecov]

Codecov Report

Merging #1682 into master will increase coverage by 0.00%.
The diff coverage is 98.50%.

@@           Coverage Diff            @@
##           master    #1682    +/-   ##
========================================
  Coverage   92.28%   92.29%            
========================================
  Files         265      265            
  Lines       19818    19928   +110     
========================================
+ Hits        18290    18393   +103     
- Misses       1099     1105     +6     
- Partials      429      430     +1     

Impacted Files	Coverage Δ
consumer/pdata/metric.go	73.72% <57.14%> (-1.75%)	⬇️
...ceiver/hostmetricsreceiver/hostmetrics_receiver.go	88.13% <75.00%> (ø)
...ceiver/internal/scraper/cpuscraper/cpu_metadata.go	100.00% <100.00%> (ø)
...eceiver/internal/scraper/cpuscraper/cpu_scraper.go	100.00% <100.00%> (ø)
...r/internal/scraper/cpuscraper/cpu_scraper_linux.go	100.00% <100.00%> (ø)
...iver/internal/scraper/diskscraper/disk_metadata.go	100.00% <100.00%> (ø)
...nternal/scraper/diskscraper/disk_scraper_others.go	100.00% <100.00%> (ø)
...l/scraper/diskscraper/disk_scraper_others_linux.go	100.00% <100.00%> (ø)
...l/scraper/filesystemscraper/filesystem_metadata.go	100.00% <100.00%> (ø)
...al/scraper/filesystemscraper/filesystem_scraper.go	100.00% <100.00%> (ø)
... and 21 more

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[james-bebbington]

Nvm - ignore all my previous comments.

The distinction between a Gauge and a non-monotomic Cumulative is:

• A Cumulative can be used in any case where measurements are added: e.g. when data is written to disk, +some bytes, when data is deleted from disk, -some bytes
• A Gauge is reserved for cases where the data source is not a sum or is not known, e.g. CPU Load (which is a moving average)

With that context, this all looks good.