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-5.wat

@@ -0,0 +1,11 @@
+(module
+  (func (export "foo")
+    i32.const 1
+    i64.const 2
+    ;; More params than results.
+    (block (param i32 i64) (result i32)
+      drop
+    )
+    drop
+  )
+)