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.wat

@@ -0,0 +1,7 @@
+(module
+  (type $ft (func (param f32) (result i32)))
+  (func $foo (export "foo") (param i32 f32) (result i32)
+    (call_indirect (type $ft) (get_local 1) (get_local 0))
+  )
+  (table (;0;) 23 23 anyfunc)
+)