Was omitted when T0 is a MAX6675.

to have it ready to display errors during (temperature)-setup.

- The command parser now displays “unknown command” in more cases.
Known commands must be added to the `switch` inside `process_commands`
to suppress the error.

- Affects code size when automatic bed leveling is enabled

Makes the output on the LCD adjustable.

- Use a global pointer for the current sanitized command
- Pre-sanitize the current command to bypass `N` and nullify `*`,
removing the need for handlers to bypass, ignore, or nullify these
parts, and reducing overhead for `code_seen`, etc.
- Pre-skip leading whitespace.
- Only look for G, M, T codes at the start of the command.
- Verify that G, M, T codes are followed by command codes.

- For better encapsulation add inlines for each prepare_move type
- Move controllerFan vars inside the function as statics
- Some formatting cleanup
- Rename `ClearToSend` as `ok_to_send`