wasi: fix symlink-related issues with path handling

[evacchi]

• Fixes a bug in handling the buffer when the write goes over the given limit. ERANGE should be returned.
• Removes dependency from the syscall package in fs.go, experimentalsys.O_WRONLY should be used instead (portability)

[evacchi]

• symlink_filestat

  ==> wasi_snapshot_preview1.path_filestat_get(fd=5,flags=,path=symlink)
  <== (filestat={filetype=SYMBOLIC_LINK,size=4,mtim=1692707577959674593},errno=ESUCCESS)
  thread 'main' panicked at 'assertion failed: `(left == right)`
    left: `1692707577959674593`,
   right: `1692707577959674393`: symlink mtim should change', src/bin/symlink_filestat.rs:46:5
  
  
      // Check that symlink mtim motification worked
      let modified_sym_stat = wasi::path_filestat_get(dir_fd, 0, "symlink")
          .expect("reading file stats after path_filestat_set_times");
      assert_eq!(
          modified_sym_stat.mtim, sym_new_mtim,
          "symlink mtim should change"
      );
  

utimens actually supports a NOFOLLOW flag, that we were using originally; the rationale for not using utimens(flag) is described in #1588

however, it seems like the workaround is actually resolving the link.

On Linux, the proprietary flag O_PATH seems to do what we want:
https://man7.org/linux/man-pages/man2/open.2.html

Obtain a file descriptor that can be used for two
purposes: to indicate a location in the filesystem tree
and to perform operations that act purely at the file
descriptor level. The file itself is not opened, and
other file operations (e.g., read(2), write(2), fchmod(2),
fchown(2), fgetxattr(2), ioctl(2), mmap(2)) fail with the
error EBADF.

...but this is obviously non-portable.

[evacchi]

repurposing this PR to only fix the actual issues, dropping the edge cases for path handling and resolution in symlinks for now.

[mathetake]

good call!