wiggle: make wasmtime a mandatory dep, get rid of own Trap enum (#5137)

* wiggle: no longer need to guard wasmtime integration behind a feature

this existed so we could use wiggle in lucet, but lucet is long EOL

* replace wiggle::Trap with wiggle::wasmtime_crate::Trap

* wiggle tests: unwrap traps because we cant assert_eq on them

* wasi-common: emit a wasmtime::Trap instead of a wiggle::Trap

formally add a dependency on wasmtime here to make it obvious, though
we do now have a transitive one via wiggle no matter what (and therefore
can get rid of the default-features=false on the wiggle dep)

* wasi-nn: use wasmtime::Trap instead of wiggle::Trap

there's no way the implementation of this func is actually
a good idea, it will panic the host process on any error,
but I'll ask @mtr to fix that

* wiggle test-helpers examples: fixes

* wasi-common cant cross compile to wasm32-unknown-emscripten anymore

this was originally for the WASI polyfill for web targets. Those days
are way behind us now.

* wasmtime wont compile for armv7-unknown-linux-gnueabihf either

crates/wiggle/tests/variant.rs

@@ -134,9 +134,10 @@ impl GetTagExercise {
             &host_memory,
             self.input_loc.ptr as i32,
             self.return_loc.ptr as i32,
-        );
+        )
+        .unwrap();
 
-        assert_eq!(e, Ok(types::Errno::Ok as i32), "get_tag errno");
+        assert_eq!(e, types::Errno::Ok as i32, "get_tag errno");
 
         let return_val: types::Excuse = host_memory
             .ptr(self.return_loc.ptr)
@@ -218,9 +219,10 @@ impl ReasonMultExercise {
             &host_memory,
             self.input_loc.ptr as i32,
             self.multiply_by as i32,
-        );
+        )
+        .unwrap();
 
-        assert_eq!(e, Ok(types::Errno::Ok as i32), "reason_mult errno");
+        assert_eq!(e, types::Errno::Ok as i32, "reason_mult errno");
 
         match self.input {
             types::Reason::DogAte(f) => {