test cases: @intcast on vector

Closes ziglang#11770

Author: wooster0

test/cases/compile_errors/@intCast_on_vec.zig

@@ -0,0 +1,10 @@
+export fn entry() void {
+    const a = @Vector(4, u32){ 1, 1, 1, 1 };
+    _ = @intCast(u32, a);
+}
+
+// error
+// backend=stage2
+// target=native
+//
+// :3:23: error: expected type 'u32', found '@Vector(4, u32)'