feat: support fallback to fstatat64 when statx is not available on Linux

[Lzzzzzt]

This PR basically support fallback to fstat64 when statx is not available on Linux.

Change to do the raw syscall of statx, which does not have requirements of libc, if this syscall failed with ENOSYS then fallback to the fstatat64

[Copilot]

Pull Request Overview

This PR adds fallback support for systems where the statx system call is not available on Linux by falling back to fstatat64. The implementation uses raw syscalls to avoid libc dependencies and includes optimizations to I/O operations and testing infrastructure.

• Implements fallback from statx to fstatat64 when statx returns ENOSYS or ENOTSUP
• Uses raw syscalls instead of libc wrappers to avoid dependency issues
• Adds comprehensive test coverage for AsyncWriteRent and AsyncReadRent implementations
• Includes various code quality improvements and optimizations

Reviewed Changes

Copilot reviewed 21 out of 21 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
monoio/src/driver/op/statx.rs	Core implementation of statx fallback logic with raw syscalls
monoio/src/fs/metadata/unix.rs	Adds From trait implementation for libc::stat64
monoio/src/fs/metadata/mod.rs	Implements fallback logic in metadata functions
monoio/src/fs/file/unix.rs	Implements fallback logic for file metadata operations
monoio/src/io/async_write_rent.rs	Adds AsyncWriteRent implementations for Cursor and Box types
monoio/src/io/async_read_rent.rs	Improves AsyncReadRent implementation for mutable slices
monoio/tests/*.rs	Adds comprehensive test coverage for new functionality
monoio/src/utils/slab.rs	Performance optimization using is_multiple_of
Various other files	Code quality improvements and documentation updates

[Lzzzzzt]

resolve #360

[Lzzzzzt]

also change the unmaintained crate fxhash to rustc-hash