crates/tui: Simple refactor

[livingsilver94]

This is mostly code style you may not agree with, but I think the replacement of the reader and writer wrappers is a win.

• TermSize now implements the Default trait, and the previous get_size() function is now TermSize's constructor.
• ProgressReader and ProgressWriter are replaced by indicatif's wrap_read() and wrap_write():
  • Shorter code
  • Prevents a previously possible division by zero
  • Those wrapper expose more methods than read() and write() for convenience