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/icall-simd.wat

@@ -0,0 +1,7 @@
+(module
+  (type $ft (func (param v128) (result v128)))
+  (func $foo (export "foo") (param i32) (param v128) (result v128)
+    (call_indirect (type $ft) (local.get 1) (local.get 0))
+  )
+  (table (;0;) 23 23 anyfunc)
+)