Add buffering for input stream and screen updates

[MightyPork]

Currently each character is sent to the parser state machine individually and each access to the screen generates an individual screen update event (and a socket broadcast).

This is wasteful.

We can buffer those for some time and then process sequentially. That could be done with a buffer, and trigger the event / parser when

(a) some time passes (20 ms?)
(b) the buffer is full

The ESP is fast so this is not really a big deal and can be left as is, but we can do better

[MightyPork]

Implemented in sending from ESP to screen with throttling, still not implemented for USART rx.
Probably a waste of time to try to improve that, the UART is slow and we're fast.

Closing until a real performance issue arises.