cranelift: move wasmtests in cranelift-wasm

Move test data used by cranelift-wasm's tests in
the crate directory, to make the tests autonomous.

Fixes #2910

cranelift/wasm/wasmtests/multi-11.wat

@@ -0,0 +1,7 @@
+(module
+  (func (export "multiLoop") (param i64) (result i64 i64)
+    (local.get 0)
+    ;; Fewer params than results.
+    (loop (param i64) (result i64 i64)
+      i64.const 42
+      return)))