Re-attempt to delete temporary upload if the file is locked by another process

[zeripath]

Fix #12339

Signed-off-by: Andrew Thornton art27@cantab.net

[silverwind]

File deletion on Windows can be a pain with the locking. I wonder if there are any third-party golang modules similar to https://github.com/isaacs/rimraf/blob/master/rimraf.js that deal with the various error scenarios.

[zeripath]

Fine. Let's do this properly - replace all uses of os.Remove / os.RemoveAll with util.Remove / util.RemoveAll which will reattempt on certain errors.

[codecov-commenter]

Codecov Report

Merging #12447 into master will decrease coverage by 0.00%.
The diff coverage is 32.14%.

@@            Coverage Diff             @@
##           master   #12447      +/-   ##
==========================================
- Coverage   43.80%   43.79%   -0.01%     
==========================================
  Files         630      631       +1     
  Lines       69821    69851      +30     
==========================================
+ Hits        30585    30594       +9     
- Misses      34300    34311      +11     
- Partials     4936     4946      +10     

Impacted Files	Coverage Δ
cmd/doctor.go	0.00% <0.00%> (ø)
cmd/dump.go	1.04% <0.00%> (-0.02%)	⬇️
models/admin.go	80.85% <0.00%> (ø)
models/attachment.go	57.74% <0.00%> (-1.41%)	⬇️
models/migrations/v112.go	0.00% <0.00%> (ø)
models/migrations/v115.go	0.00% <0.00%> (ø)
models/migrations/v96.go	0.00% <0.00%> (ø)
models/org.go	73.61% <0.00%> (ø)
models/repo.go	55.56% <0.00%> (ø)
models/upload.go	0.00% <0.00%> (ø)
... and 40 more

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