Support for fread() of file:// URI with spaces

[MichaelChirico]

Closes #7550.

[MichaelChirico]

I also confirm we can't use URLencode() (to avoid special-casing file://)

readLines(URLencode(u))
# Error in file(con, "r") : cannot open the connection
# In addition: Warning message:
# In file(con, "r") :
#   cannot open file '/tmp/RtmpyAROdr/a%20dir/a.csv': No such file or directory

And that https? URIs will not have this issue:

https://stackoverflow.com/a/497972/3576984

I can't quite confirm the situation for ftps? URIs, but it seems like they might support spaces? I'm happy to punt until there's an actual user report, though.

[github-actions]

• HEAD=fread-file-spaces slower P<0.001 for setDT improved in #5427
  

Generated via commit 62cf117

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

Task	Duration
R setup and installing dependencies	2 minutes and 49 seconds
Installing different package versions	1 minutes and 7 seconds
Running and plotting the test cases	4 minutes and 24 seconds

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.96%. Comparing base (3e579ee) to head (62cf117).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #7551   +/-   ##
=======================================
  Coverage   98.96%   98.96%           
=======================================
  Files          87       87           
  Lines       16737    16737           
=======================================
  Hits        16563    16563           
  Misses        174      174           

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[ben-schwen]

LGTM TY!

[aitap]

Indeed, it was a bug. Thank you!