filecontent: report itemsRead metric

[dmivankov]

Since filecontent doesn't go through SdkV1Relation.{buildScan, getStream} to implement reads
read metrics weren't being automatically reported.

Now it will do itemsRead.inc() once per line

[Jacob-Eliat-Eliat]

Do you remember why we decided not to implement sdkV1relation? I vaguely remember discussing it but I don't remember the reasons for our decisions back then

[dmivankov]

Do you remember why we decided not to implement sdkV1relation? I vaguely remember discussing it but I don't remember the reasons for our decisions back then

Nope, don't remember any specifics, maybe it doesn't provide suitable helpers or assumes more operations that filecontent supports? But could be something to look into

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.33%. Comparing base (410e714) to head (9a6cec0).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1002   +/-   ##
=======================================
  Coverage   83.33%   83.33%           
=======================================
  Files          47       47           
  Lines        3156     3156           
  Branches      452      452           
=======================================
  Hits         2630     2630           
  Misses        526      526           

Files with missing lines	Coverage Δ
...n/scala/cognite/spark/v1/FileContentRelation.scala	95.23% <ø> (ø)