Implement File.readable? and .writable? in Win32

[HertzDevil]

Note that File.writable returns true for read-only directories, which is inconsistent with File.info; this has always been the case for the original LibC._waccess_s, this PR merely exposes this fact in Crystal code.

[HertzDevil]

Could anyone reproduce the interpreter failures locally?

[straight-shoota]

Nope. This seems very odd. Especially that both, readable and writable are failing. Maybe a file system issue? But it would be weird to have that only in the interpreter and not in compiled mode...
I added a commit to inspect the file permissions.

[straight-shoota]

So the FS permissions definitely seem to be correct, yet the specs are still failing:

File::Permissions[OtherWrite, GroupWrite, OwnerWrite]F
File::Permissions[OtherRead, GroupRead, OwnerRead]F

I pushed another commit to see what happens for 0o000 permissions.

[straight-shoota]

Interestingly, in the latest run there's only one failure: https://github.com/crystal-lang/crystal/actions/runs/8551832454/job/23432079701?pr=14420

[HertzDevil]

Turns out this was just #13217 and compiled code would have had the same issue, CI didn't notice because we pass -u 1001 to Docker

[straight-shoota]

Doh 🤦 Yeah that makes a lot of sense. Great find!