fread with col.names and drop

[ben-schwen]

Closes #3459

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.03%. Comparing base (b0b8b23) to head (6719e11).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7493      +/-   ##
==========================================
- Coverage   99.04%   99.03%   -0.01%     
==========================================
  Files          87       87              
  Lines       16678    16694      +16     
==========================================
+ Hits        16518    16533      +15     
- Misses        160      161       +1     

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[github-actions]

No obvious timing issues in HEAD=fread_colnames_drop

Generated via commit 6719e11

Download link for the artifact containing the test results: ↓ atime-results.zip

Task	Duration
R setup and installing dependencies	4 minutes and 59 seconds
Installing different package versions	11 minutes and 4 seconds
Running and plotting the test cases	5 minutes and 5 seconds