Remove FILEDosToUnixPathA conversion

[janvorli]

All file paths passed to the coreclr PAL are processed by this function to convert backslash characters to forward ones. This is causing problems when users have directories with names containing backslashes. Such problems were recently reported by people.

This change removes the FILEDosToUnixPathA and fixes one PAL test and one coreclr test that was passing backslash separated paths.

[jkotas]

There are a few places in the runtime that have similar problem. Could you please scan and fix them as well?

For example,

runtime/src/coreclr/utilcode/splitpath.cpp

Line 111 in 2f9418d

if (*p == _T('/') || *p == _T('\\'))

[ghost]

Added needs-breaking-change-doc-created label because this PR has the breaking-change label.

When you commit this breaking change:

1. Create and link to this PR and the issue a matching issue in the dotnet/docs repo using the breaking change documentation template, then remove this needs-breaking-change-doc-created label.
2. Ask a committer to mail the .NET Breaking Change Notification DL.

Tagging @dotnet/compat for awareness of the breaking change.

[jkotas]

This needs to be tracked as a breaking change.

[AaronRobinsonMSFT]

@elinor-fung Isn't there an issue that is tracking this behavior?

[elinor-fung]

There may be others, but #75387 is the one I know of (with some other issues closed as duplicates against it).

[MichalStrehovsky]

NativeAOT is also emulating this:

runtime/src/coreclr/nativeaot/System.Private.CoreLib/src/System/Runtime/InteropServices/NativeLibrary.NativeAot.Unix.cs

Lines 14 to 15 in 1076cf5

	// do the Dos/Unix conversion
	libraryName = libraryName.Replace('\\', '/');

[janvorli]

@jkotas, @AaronRobinsonMSFT I have scanned the whole coreclr and nativeaot and modified all places where we were either converting the directory separators, or using both or even using backslashes on Unix too. And I've removed
_wsplitpath_s.

[janvorli]

The AppHost.Bundle.Tests.BundleExtractToSpecificPath.Bundle_Extraction_To_Relative_Path_Succeeds fails with these changes for this [InlineData("foo\\bar", BundleOptions.BundleNativeBinaries)]. This test case should be Windows specific after this change as it expects the foo and bar to be separate directories. We already have an exclusion check for similar case with forward slash on Windows, so I will mimic that.

[janvorli]

@jkotas, @AaronRobinsonMSFT the CI is green and I believe I have addressed all of the feedback. I'll merge it in the morning unless you have an additional feedback.

[janvorli]

The breaking change issue is here: dotnet/docs#32906