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/pointers.rs

@@ -155,8 +155,9 @@ impl PointersAndEnumsExercise {
             self.input2_loc.ptr as i32,
             self.input3_loc.ptr as i32,
             self.input4_ptr_loc.ptr as i32,
-        );
-        assert_eq!(e, Ok(types::Errno::Ok as i32), "errno");
+        )
+        .unwrap();
+        assert_eq!(e, types::Errno::Ok as i32, "errno");
 
         // Implementation of pointers_and_enums writes input3 to the input2_loc:
         let written_to_input2_loc: i32 = host_memory