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/simd.wat

@@ -0,0 +1,29 @@
+(module
+  (func $test_splat (result i32)
+    i32.const 42
+    i32x4.splat
+    i32x4.extract_lane 0
+  )
+
+  (func $test_insert_lane (result i32)
+      v128.const i64x2 0 0
+      i32.const 99
+      i32x4.replace_lane 1
+      i32x4.extract_lane 1
+  )
+
+  (func $test_const (result i32)
+    v128.const i32x4 1 2 3 4
+    i32x4.extract_lane 3
+  )
+
+  (func $test_locals (local i32 v128)
+    local.get 0
+    i32x4.splat
+    local.set 1
+  )
+
+  (export "test_splat" (func $test_splat))
+  (export "test_insert_lane" (func $test_insert_lane))
+  (export "test_const" (func $test_const))
+)