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/fac-multi-value.wat

@@ -0,0 +1,19 @@
+(module
+  ;; Iterative factorial without locals.
+  (func $pick0 (param i64) (result i64 i64)
+    (get_local 0) (get_local 0)
+  )
+  (func $pick1 (param i64 i64) (result i64 i64 i64)
+    (get_local 0) (get_local 1) (get_local 0)
+  )
+  (func (export "fac-ssa") (param i64) (result i64)
+    (i64.const 1) (get_local 0)
+    (loop $l (param i64 i64) (result i64)
+      (call $pick1) (call $pick1) (i64.mul)
+      (call $pick1) (i64.const 1) (i64.sub)
+      (call $pick0) (i64.const 0) (i64.gt_u)
+      (br_if $l)
+      (drop) (return)
+    )
+  )
+)