fix(console): wrap controls line when the terminal is too narrow

[hawkw]

Currently, the controls line for table views is never wrapped, even if
it's too long to fit on a single line in the current terminal width.
This isn't great...especially since PR #223 is adding more controls, and
will make the line even longer.

This branch allows wrapping the controls paragraph if it doesn't fit in
the current area. The code for this was surprisingly complex: while
tui supports wrapping text, layout area sizes are determined before
text wrapping. So, we can't just say "use as many lines as are necessary
to fit this text in the current terminal width", we have to implement
that logic ourselves, and pass the required number of lines to the
Layout::constraints method.

Screenshots

On the main branch, we don't wrap. Here's a wide enough terminal:

...and here's one that's too narrow:

After this change, when the terminal is wide enough, it looks the same:

...but if the terminal is too narrow, it wraps:

It might be nice to change this code to only wrap on commas, so each
<keys> = <description> isn't broken...but that seems like a lot more
work than just wrapping on whitespace, and the current thing is better
than it was before!

[zaharidichev]

Nice!