Refactor longpress text when it's generated by Id

Currently on the touch layout, longpress for K_SPACE causes the app to crash because it is attempting to parse `K_SPACE` as an int for generating the longpress text.

- Clean up when key text is empty how it is parsed from Id
-Change Unicode hex string delimiter from `,0x` to `\\u` which makes it easier to read `executePopupKey()` in the logs.