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/generate/src/funcs.rs

@@ -91,7 +91,7 @@ fn _define_func(
                     ctx: &mut (impl #(#bounds)+*),
                     memory: &dyn #rt::GuestMemory,
                     #(#abi_params),*
-                ) -> Result<#abi_ret, #rt::Trap> {
+                ) -> Result<#abi_ret, #rt::wasmtime_crate::Trap> {
                     use std::convert::TryFrom as _;
                     #mk_span
                     _span.in_scope(|| {
@@ -109,7 +109,7 @@ fn _define_func(
                     ctx: &'a mut (impl #(#bounds)+*),
                     memory: &'a dyn #rt::GuestMemory,
                     #(#abi_params),*
-                ) -> impl std::future::Future<Output = Result<#abi_ret, #rt::Trap>> + 'a {
+                ) -> impl std::future::Future<Output = Result<#abi_ret, #rt::wasmtime_crate::Trap>> + 'a {
                     use std::convert::TryFrom as _;
                     use #rt::tracing::Instrument as _;
                     #mk_span

crates/wiggle/generate/src/lib.rs

@@ -43,7 +43,7 @@ pub fn generate(doc: &witx::Document, names: &Names, settings: &CodegenSettings)
         let abi_typename = names.type_ref(&errtype.abi_type(), anon_lifetime());
         let user_typename = errtype.typename();
         let methodname = names.user_error_conversion_method(&errtype);
-        quote!(fn #methodname(&mut self, e: super::#user_typename) -> Result<#abi_typename, #rt::Trap>;)
+        quote!(fn #methodname(&mut self, e: super::#user_typename) -> Result<#abi_typename, #rt::wasmtime_crate::Trap>;)
     });
     let user_error_conversion = quote! {
         pub trait UserErrorConversion {

crates/wiggle/generate/src/module_trait.rs

@@ -45,7 +45,7 @@ pub fn define_module_trait(names: &Names, m: &Module, settings: &CodegenSettings
         });
 
         let result = match f.results.len() {
-            0 if f.noreturn => quote!(#rt::Trap),
+            0 if f.noreturn => quote!(#rt::wasmtime_crate::Trap),
             0 => quote!(()),
             1 => {
                 let (ok, err) = match &**f.results[0].tref.type_() {

crates/wiggle/generate/src/wasmtime.rs

@@ -121,11 +121,7 @@ fn generate_func(
         let (mem , ctx) = mem.data_and_store_mut(&mut caller);
         let ctx = get_cx(ctx);
         let mem = #rt::wasmtime::WasmtimeGuestMemory::new(mem);
-        match #abi_func(ctx, &mem #(, #arg_names)*) #await_ {
-            Ok(r) => Ok(<#ret_ty>::from(r)),
-            Err(#rt::Trap::String(err)) => Err(#rt::wasmtime_crate::Trap::new(err)),
-            Err(#rt::Trap::I32Exit(err)) => Err(#rt::wasmtime_crate::Trap::i32_exit(err)),
-        }
+        Ok(<#ret_ty>::from(#abi_func(ctx, &mem #(, #arg_names)*) #await_ ?))
     };
 
     match asyncness {