virtiofs: Fix POSIX filesystem compatibility issues

[damanm24]

I ran the following POSIX Filesystem compatibility test: https://github.com/zfsonlinux/fstest against our virtiofs implementation (with the metadata option enabled) which surfaced a couple of errors:

1. Returning incorrect/non-specific error codes:
   https://github.com/zfsonlinux/fstest/blob/master/tests/rmdir/06.t
   https://github.com/zfsonlinux/fstest/blob/master/tests/open/03.t

2. Edge cases when handling clearing/setting uid/gid bits on files/directories
   https://github.com/zfsonlinux/fstest/blob/master/tests/chown/00.t (Specifically a couple of the assertions between 64-94)

This PR fixes these issues, and with the changes the test suite passes all testcases except for 1 related to setting the file size to a large value (999 TiB) see: https://github.com/zfsonlinux/fstest/blob/master/tests/truncate/12.t

[github-actions]

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[Copilot]

Pull request overview

This PR fixes POSIX filesystem compatibility issues in the virtiofs implementation, as identified by running the zfsonlinux fstest suite. The changes address incorrect error code mappings, edge cases in setuid/setgid bit handling, and add validation for filename lengths.

Changes:

• Map Windows STATUS_CANNOT_DELETE to ENOTEMPTY instead of EIO for more accurate directory deletion errors
• Fix chown(-1, -1) behavior to properly distinguish between regular files and directories when clearing setuid/setgid bits
• Add NAME_MAX validation (255 bytes) for FUSE file name components with appropriate ENAMETOOLONG error

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
vm/devices/support/fs/lxutil/src/windows/util.rs	Updates error code mapping for STATUS_CANNOT_DELETE and fixes setuid/setgid clearing logic for chown(-1, -1) to distinguish between files and directories
vm/devices/support/fs/lxutil/src/windows/mod.rs	Adds additional error codes to the list that bypass the read-only file workaround during deletion
vm/devices/support/fs/lxutil/src/windows/fs.rs	Adds additional error codes to the list that bypass the read-only file workaround during deletion
vm/devices/support/fs/fuse/src/session.rs	Adds handler for new FuseOperation::Error variant to return specific parsing errors
vm/devices/support/fs/fuse/src/request/macros.rs	Adds Error variant to FuseOperation enum and implements Debug for it
vm/devices/support/fs/fuse/src/request.rs	Changes Invalid to Error variant when parsing fails with specific error, and adds NAME_MAX validation for filenames