Fixes for windows & enable in CI

[kipz]

Since windows tests were disabled, it looks like we've drifted a bit and introduced a few issues preventing the tests from passing and from the project working on windows:

• use of unix path separators throughout
• tests relying on line endings, and Git checkouts being different for windows/linux
• renaming of files between drives on windows on GitHub Actions
• renaming of open files (not allowed on windows)

Moved from rdimitrov/go-tuf-metadata#98

EDIT

• Maybe merge this one first so that this PR can be tested properly: Replace main with master in workflows #587

[codecov-commenter]

Codecov Report

Attention: 39 lines in your changes are missing coverage. Please review.

Comparison is base (8391850) 71.43% compared to head (14cda1b) 70.28%.

Files	Patch %	Lines
metadata/updater/updater.go	22.00%	35 Missing and 4 partials ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #586      +/-   ##
==========================================
- Coverage   71.43%   70.28%   -1.15%     
==========================================
  Files          10       10              
  Lines        2013     2063      +50     
==========================================
+ Hits         1438     1450      +12     
- Misses        463      497      +34     
- Partials      112      116       +4     

Flag	Coverage Δ
Go-1.21	70.28% <22.00%> (-1.15%)	⬇️

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[rdimitrov]

Looks great! 🚀

[kommendorkapten]

Nice one 🪟