Fix copy ignore_case on Windows

[uilianries]

Changelog: Fix: self.copy() follows igore_case correctly on Windows.
Docs: conan-io/docs#1862

This PR fixes self.copy(ignore_case=True/False) on Windows. The actual behavior, on Windows, ignore_case=False doesn't work.

Fixes #6116

UPDATE:

• ignore_case=True should be the default, because it's very old bug, and a fix right now would break Windows users.

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[memsharded]

This is broken, filter is doing internally some os.path.normcase, which changes / => \ path in Windows too

[memsharded]

I am seeing this possibly breaking users, because it is by default ignoring case.
Agree it is a bug, but as most users haven't had to specify it, I would say that the bug is in the default. The default should be ignore_case=True, and then alter the behavior if it is explicitly changed to ignore_case=False. Wdyt?

[uilianries]

Sounds good to me, indeed that's the original behavior, and changing it only after 4 years of project, probably will break users. I'll update this PR to use ignore_case=True by default.

[uilianries]

About filter, thanks for checking it, I'll search a better way.

[uilianries]

@memsharded I've split both comparisons, now for non-case-sensitive, it will keep the old behavior, as fnmatch.filter changes all file names to lower-case in Windows due normcase. For case-sensitive check, I kept same modification, but normalizing the path with normpath.