Auto-generate the hostcalls module of wasi-common (#846)

* Auto-generate shims for old `wasi_unstable` module

This commit is effectively just doing what #707 already did, but
applying it to the `snapshot_0` module as well. The end result is the
same, where we cut down on all the boilerplate in `snapshot_0` and bring
it in line with the main `wasi_snapshot_preview1` implementation. The
goal here is to make it easier to change the two in tandem since they're
both doing the same thing.

* Migrate `wasi_common::hostcalls` to a macro

This commit migrates the `hostcalls` module to being auto-generated by a
macro rather than duplicating a handwritten signature for each wasi
syscall.

* Auto-generate snapshot_0's `hostcalls` module

Similar to the previous commit, but for `snapshot_0`

* Delete the `wasi-common-cbindgen` crate

This is no longer needed with the hostcalls macro now, we can easily
fold the definition of the cbindgen macro into the same crate.

* Rustfmt

* Fix windows build errors

* Rustfmt

* Remove now no-longer-necessary code

* rustfmt

crates/wasi-common/src/fs/file.rs

@@ -1,5 +1,5 @@
-use crate::fs::{error::wasi_errno_to_io_error, Metadata};
-use crate::{host, hostcalls, wasi, WasiCtx};
+use crate::fs::Metadata;
+use crate::{host, hostcalls, hostcalls_impl, wasi, Result, WasiCtx};
 use std::io;
 
 /// A reference to an open file on the filesystem.
@@ -34,8 +34,11 @@ impl<'ctx> File<'ctx> {
     /// This corresponds to [`std::fs::File::sync_all`].
     ///
     /// [`std::fs::File::sync_all`]: https://doc.rust-lang.org/std/fs/struct.File.html#method.sync_all
-    pub fn sync_all(&self) -> io::Result<()> {
-        wasi_errno_to_io_error(unsafe { hostcalls::fd_sync(self.ctx, &mut [], self.fd) })
+    pub fn sync_all(&self) -> Result<()> {
+        unsafe {
+            hostcalls_impl::fd_sync(self.ctx, &mut [], self.fd)?;
+        }
+        Ok(())
     }
 
     /// This function is similar to `sync_all`, except that it may not synchronize
@@ -44,8 +47,11 @@ impl<'ctx> File<'ctx> {
     /// This corresponds to [`std::fs::File::sync_data`].
     ///
     /// [`std::fs::File::sync_data`]: https://doc.rust-lang.org/std/fs/struct.File.html#method.sync_data
-    pub fn sync_data(&self) -> io::Result<()> {
-        wasi_errno_to_io_error(unsafe { hostcalls::fd_datasync(self.ctx, &mut [], self.fd) })
+    pub fn sync_data(&self) -> Result<()> {
+        unsafe {
+            hostcalls_impl::fd_datasync(self.ctx, &mut [], self.fd)?;
+        }
+        Ok(())
     }
 
     /// Truncates or extends the underlying file, updating the size of this file
@@ -54,10 +60,11 @@ impl<'ctx> File<'ctx> {
     /// This corresponds to [`std::fs::File::set_len`].
     ///
     /// [`std::fs::File::set_len`]: https://doc.rust-lang.org/std/fs/struct.File.html#method.set_len
-    pub fn set_len(&self, size: u64) -> io::Result<()> {
-        wasi_errno_to_io_error(unsafe {
-            hostcalls::fd_filestat_set_size(self.ctx, &mut [], self.fd, size)
-        })
+    pub fn set_len(&self, size: u64) -> Result<()> {
+        unsafe {
+            hostcalls_impl::fd_filestat_set_size(self.ctx, &mut [], self.fd, size)?;
+        }
+        Ok(())
     }
 
     /// Queries metadata about the underlying file.
@@ -65,7 +72,7 @@ impl<'ctx> File<'ctx> {
     /// This corresponds to [`std::fs::File::metadata`].
     ///
     /// [`std::fs::File::metadata`]: https://doc.rust-lang.org/std/fs/struct.File.html#method.metadata
-    pub fn metadata(&self) -> io::Result<Metadata> {
+    pub fn metadata(&self) -> Result<Metadata> {
         Ok(Metadata {})
     }
 }