Normalize default metrics

[phnx47]

Rename metrics:

process_virtual_bytes -> process_virtual_memory_bytes
process_private_bytes -> process_private_memory_bytes
process_working_set -> process_working_set_bytes
dotnet_totalmemory -> dotnet_total_memory_bytes

Add metrics:

process_open_handles

Should be compatible with https://grafana.com/grafana/dashboards/10427

[codecov]

Codecov Report

Merging #190 (1861869) into master (0212d93) will increase coverage by 0.57%.
The diff coverage is 87.50%.

❗ Current head 1861869 differs from pull request most recent head fce4699. Consider uploading reports for the commit fce4699 to get more accurate results

@@            Coverage Diff             @@
##           master     #190      +/-   ##
==========================================
+ Coverage   87.34%   87.91%   +0.57%     
==========================================
  Files          48       48              
  Lines        1691     1746      +55     
  Branches      228      234       +6     
==========================================
+ Hits         1477     1535      +58     
+ Misses        164      161       -3     
  Partials       50       50              

Impacted Files	Coverage Δ
.../Prometheus.Client/Collectors/DefaultCollectors.cs	50.00% <20.00%> (+50.00%)	⬆️
...lectors/DotNetStats/CollectorRegistryExtensions.cs	50.00% <20.00%> (+50.00%)	⬆️
...ectors/ProcessStats/CollectorRegistryExtensions.cs	50.00% <25.00%> (+50.00%)	⬆️
...llectors/DotNetStats/GCCollectionCountCollector.cs	100.00% <100.00%> (+4.54%)	⬆️
...t/Collectors/DotNetStats/GCTotalMemoryCollector.cs	100.00% <100.00%> (+7.69%)	⬆️
...Client/Collectors/ProcessStats/ProcessCollector.cs	100.00% <100.00%> (+2.50%)	⬆️
... and 1 more

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[phnx47]

@sanych-sun Hi, any ideas on how we can collect these metrics?

process_resident_memory_bytes
process_open_fds
process_max_fds

[phnx47]

I'm not sure about process_processid, maybe better rename it to process_id?

[sanych-sun]

"fds" - is it count of open file descriptors? If so, not sure if it's possible without pinvoke. We might want to report Process.HandleCount, but this count includes any kind of handle, not just open files.

[phnx47]

process_open_fds - Number of open file descriptors
process_max_fds - Maximum number of open file descriptors
process_resident_memory_bytes - Resident memory size in bytes

I found these metrics in Go and Java client

[phnx47]

I will come back to this task soon