Fix incomplete support for stderr in Legacy Windows layer

[Jackenmen]

Type of changes

• Bug fix
• New feature
• Documentation / docstrings
• Tests
• Other

AI?

• AI was used to generate this PR

Checklist

• I've run the latest black with default args on new code.
• I've updated CHANGELOG.md and CONTRIBUTORS.md where appropriate (see note about typos above).
• I've added tests for new code.
• I accept that @willmcgugan may be pedantic in the code review.

Description

I've grepped through the code for argless calls to GetStdHandle() and, where appropriate, I've updated them to use the stderr handle (-12 per https://learn.microsoft.com/en-us/windows/console/getstdhandle#parameters), when operating on stderr.
Specifically:

• Console now detects terminal features for stderr correctly, when stdout is redirected (before, stderr was always treated as legacy Windows when stdout is redirected, even if stderr was attached to Windows Terminal, not conhost)
• Console(stderr=True, legacy_windows=True) now actually operates on stderr for features that require Windows Console API instead of stdout
• public get_windows_console_features() and detect_legacy_windows() functions in rich.console module now accept an optional file argument

I didn't write any tests because it does not seem like the functions/methods that I edited had any existing ones. I assume that means it's probably okay, and I don't exactly have a good idea of what would need to be tested here anyway.

You'll notice I moved the legacy_windows assignment to the end of the init function. This was needed because I had to be able to pass self.file to detect_legacy_windows(). The width, height, and color system detection depend on its value, so they had to be moved as well.

Fixes #4071

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Codecov Report

❌ Patch coverage is 87.87879% with 4 lines in your changes missing coverage. Please review.
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Files with missing lines	Patch %	Lines
rich/_win32_console.py	71.42%	4 Missing ⚠️
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Additional details and impacted files

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Flag	Coverage Δ
unittests	97.77% <87.87%> (?)

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[Jackenmen]

Sorry for a bit of churn, I struggled with appeasing mypy a bit...
This part in particular is a bit annoying, but I couldn't think of a better way to avoid mypy reporting an issue here:
b159cea

I guess strictly speaking, STDERR_FILENO and STDOUT_FILENO are used both in console and _win32_console module - let me know if I should just create a new module for them (module name suggestions welcome 😄).