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/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_() {