Add vi 'y' bindings and some i / a support

[joncinque]

Description

Many people have mentioned wanting support for changing / yanking /
deleting between "" and '', meaning the commands ci' ci" yi' yi" di' di",
so this adds that support in a generic, and thus potentially confusing way.
The concept is that we check for the character backwards and forwards
before making the selection. Unfortunately, this will also work for any
character that isn't w or W, so cia could change everything between
two a characters.
Looking through the bind documentation
and input handler at src/input.cpp,
this is the best possible solution I could come up with until
forward-jump and backward-jump can accept input in the call to bind,
and not just from stdin, meaning we can write a binding as:

bind di\" backward-jump-till \" and repeat-jump-reverse ...`

If that were done, then other commands such as di) to go between () would
be possible.
There are also some added y bindings not part of #6648.
Let me know if you need anything else.

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

[faho]

I'm not sure how useful this is - it seems like it really only works for " and ', which isn't entirely uncommon.

But on the other hand, I'm not entirely sure how to bring this into the binding system. How do we break this down?

Adding arguments to bind functions like you propose is one idea, but that complicates the already weird bind DSL.

Can we find operations that this requires, and add them so that we can then implement these things in their terms?

I think we might be able to? "di)" to me appears to require the following:

• Find the next ")" - this is just forward-jump
• Enable selection - (well, really, start a new selection. If one already exists we'd have to "stash" it or something?)
• Find the corresponding "(" - this would be "%", and would be good to have anyway. Note that this requires cooperation from the parser.
• Shrink the selection by 1 on both ends (to exclude "()")
• Delete the selection (kill-selection)

And for "di(" it would require a backward jump first or a forward-jump with the argument switched around.

---

Which just leaves the question of what we do with this now. And personally, I'd assume that pressing di" and getting something is good even if di) doesn't work.

So I'm merging this. Thanks!

[joncinque]

I think this should all be possible if forward-jump and its variants can accept input from the binding command, and not just from stdin. Given the current setup of the system, I'm not sure how that'll be feasible though. Anyway, thanks for merging this in!