Update the wasm-tools family of crates, disallow empty component types (

bytecodealliance/wasmtime#6777)

* Remove unused WIT files from Wasmtime

These files aren't actually read by anything currently. They were added
historically and a previous refactoring in #6390 forgot to remove them.
No tests or build process reads them so this deletes them to get them
out of the way.

* Update dependencies on wasm-tools crates.

This commit updates the deps on the wasm-tools family of crates to bring
in a few fixes for WIT/component-related things. Primarily though this
brings in an update to the component model where empty types are now
disallowed.

Some tests using empty types were adjusted to use non-empty types, but
many tests were also simply removed as they existed to test what would
happen with empty types which now no longer needs to be tested.

* Update `stream-error` in preview2

Add a `dummy` field to make it a non-empty structure. It's expected that
this will change to something else more "official" in the future, but
for now this is here to keep everything compiling.

* Update component fuzzing to avoid empty types

Empty types are no longer valid

* Update crates/wasi/wit/deps/io/streams.wit

Co-authored-by: Peter Huene <peter@huene.dev>

---------

Co-authored-by: Peter Huene <peter@huene.dev>

streams.wit

@@ -8,9 +8,15 @@ package wasi:io
 interface streams {
     use wasi:poll/poll.{pollable}
 
-    /// An error type returned from a stream operation. Currently this
-    /// doesn't provide any additional information.
-    record stream-error {}
+    /// An error type returned from a stream operation.
+    ///
+    /// TODO: need to figure out the actual contents of this error. Used to be
+    /// an empty record but that's no longer allowed. The `dummy` field is
+    /// only here to have this be a valid in the component model by being
+    /// non-empty.
+    record stream-error {
+      dummy: u32,
+    }
 
     /// Streams provide a sequence of data and then end; once they end, they
     /// no longer provide any further data.