Make "-q" always check for existence

[faho]

Description

Recently I had the weird experience of having to explain to someone how to check if a thing-you-can-call exists (i.e. a function, builtin, command, or any of them).

And what I had to say was:

functions -q $thing # for a function
builtin -n | string match -q $thing # for a builtin
command -sq $thing # for a command
type -q $thing # for any of the above

It seems to be a fairly straightforward improvement to usability to just add a "-q" option to all of these.

So this PR adds "-q"/"--query" to builtin and allows command -q $thing to work by making "-q" imply "-s".

For historical reasons the long form to "command" is still "--quiet", but that's not a large problem.

TODOs:

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

[ridiculousfish]

Seems fine to me, remember to relnote it