Portably handle `fd_advise` on directory fd (#2875)
This commit adds a check to `fd_advise`. If the fd is a directory,
return `ebadf`. This brings iwasm in line with Wasmtime's behavior.
WASI folks have stated that fd_advise should not work on directories
as this is a Linux-specific behavior:
https://github.com/bytecodealliance/wasmtime/issues/6505#issuecomment-1574122949