[release/6.0-rc2] File preallocationSize: align Windows and Unix behavior. (#59532)

[release/6.0-rc2] File preallocationSize: align Windows and Unix behavior. (#59532)

* Align preallocationSize behavior (#58726)

Co-authored-by: Stephen Toub <stoub@microsoft.com>
* File preallocationSize: align Windows and Unix behavior. (#59338)

* File preallocationSize: align Windows and Unix behavior.

This aligns Windows and Unix behavior of preallocationSize for the
intended use-case of specifing the size of a file that will be written.

For this use-case, the expected FileAccess is Write, and the file should be
a new one (FileMode.Create*) or a truncated file (FileMode.Truncate).
Specifing a preallocationSize for other modes, or non-writable files throws ArgumentException.

The opened file will have a length of zero, and is ready to be written to by the user.

If the requested size cannot be allocated, an IOException is thrown.

When the OS/filesystem does not support pre-allocating, preallocationSize is ignored.

* fix pal_io preprocessor checks

* pal_io more fixes

* ctor_options_as.Windows.cs: fix compilation

* Update tests

* tests: use preallocationSize from all public APIs

* pal_io: add back FreeBSD, fix OSX

* tests: check allocated is zero when preallocation is not supported.

* Only throw for not enough space errors

* Fix compilation

* Add some more tests

* Fix ExtendedPathsAreSupported test

* Apply suggestions from code review

Co-authored-by: David Cantú <dacantu@microsoft.com>
* Update System.Private.CoreLib Strings.resx

* PR feedback

* Remove GetPathToNonExistingFile

* Fix compilation

* Skip checking allocated size on mobile platforms.

Co-authored-by: David Cantú <dacantu@microsoft.com>
* Fix unused fileDescriptor

* void fd when unused

* Address feedback

Co-authored-by: Adam Sitnik <adam.sitnik@gmail.com>
Co-authored-by: Stephen Toub <stoub@microsoft.com>
Co-authored-by: Tom Deseyn <tom.deseyn@gmail.com>