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-17.wat

@@ -0,0 +1,26 @@
+(module
+  (func $main (type 0) (param i32 i32 i32) (result i32)
+    i32.const 0
+    i32.const 0
+    i32.const 0
+    i32.const 0
+
+    i32.const 0
+    if (param i32 i32 i32) (result i32)  ;; label = @1
+      br 0 (;@1;)
+    else
+      call $main
+    end
+
+    i32.const 0
+
+    i32.const 0
+    if (param i32 i32 i32) (result i32)  ;; label = @1
+      drop
+      drop
+    else
+      drop
+      drop
+    end
+  )
+  (export "main" (func $main)))