Make fish_key_reader's output simpler

[faho]

Description

fish_key_reader is mostly used to tell people how to bind a certain key combination.

However, by default it prints a lot of information that isn't useful for that and might be overwhelming:

> fish_key_reader
Press a key:
              hex:   1B  char: \c[  (or \e)
(  0.032 ms)  hex:   5B  char: [
(  0.023 ms)  hex:   31  char: 1
(  0.025 ms)  hex:   3B  char: ;
(  0.029 ms)  hex:   35  char: 5
(  0.031 ms)  hex:   41  char: A
bind \e\[1\;5A 'do something'

Really, everything I need here is the first line to tell me what to do, and the last line to tell me the information I was looking for.

Everything in between is useful for debugging, but doesn't need to be the default.

So this relegates all the timing and per-character information to a "--verbose" mode, the default output is just the bind command and instructions.

The new output looks like:

Press a key:
bind \e\[1\;5A 'do something'

TODOs:

• Changes to fish usage are reflected in user documentation/manpages.
• Tests have been added for regressions fixed
• User-visible changes noted in CHANGELOG.rst