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/if-unreachable-else-params-2.wat

@@ -0,0 +1,18 @@
+(module
+  (type (;0;) (func (param i32 i32) (result f64)))
+  (func $main (type 0) (param i32 i32) (result f64)
+    f64.const 1.0
+    local.get 0
+    local.get 1
+    if (param i32)  ;; label = @2
+      i64.load16_s align=1
+      drop
+    else
+      unreachable
+    end)
+  (table (;0;) 63 255 funcref)
+  (memory (;0;) 13 16)
+  (export "t1" (table 0))
+  (export "m1" (memory 0))
+  (export "main" (func $main))
+  (export "memory" (memory 0)))