UART: The calling order of with_tx() and with_rx() builder functions might matter

[JurajSadel]

let uart = Uart::new(peripherals.UART1, uart::Config::default())
            .unwrap()
            .with_tx(tx)
            .with_rx(rx);

and

let uart = Uart::new(peripherals.UART1, uart::Config::default())
            .unwrap()
            .with_rx(rx)
            .with_tx(tx);

could produce different results as discovered in #2132 (comment) and re-appeared in #2904.

Affected chip: ESP32