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 https://github.com/rdimitrov/go-tuf-metadata/pull/98

EDIT

• Maybe merge this one first so that this PR can be tested properly: https://github.com/theupdateframework/go-tuf/pull/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 :warning:

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Additional details and impacted files

```diff @@ 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](https://app.codecov.io/gh/theupdateframework/go-tuf/pull/586/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=theupdateframework) | Coverage Δ | | |---|---|---| | [Go-1.21](https://app.codecov.io/gh/theupdateframework/go-tuf/pull/586/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=theupdateframework) | `70.28% <22.00%> (-1.15%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=theupdateframework#carryforward-flags-in-the-pull-request-comment) to find out more.

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