[opentitanlib] Refactor UartConsole to a plugin-based design

[sasdf]

This PR refactors UartConsole by extracting complex functionalities into dedicated plugin middleware modules, simplifying its core logic.

[nbdd0121]

Instead of plugins, I would like to get rid of UartConsole completely. It currently has a few features today:

• Interacting through stdin -- this is only used by opentitantool console, and should just be implemented there instead.
• Waiting for status -- this should just be an utility function that takes dyn Uart and performs the wait
• Printing to the log -- this should be a middleware that also implements Uart which is just a wrapper, it passes data through and internally performs line-buffering; when a whole line is received it gets printed.

Coverage would also, in my opinion, just be a middleware that implements Uart and passes everything through apart from poll_read.