Update orderless-escapable-split-on-space to support other characters

[dadinn]

Allows customising the escapable component separator character to be other than just a space. This feature was originally requested/discussed here.

Introduces a new customisable variable orderless-escapable-separator, which allows any character to be used as separator, not just the default space character (to be backwards compatible).

Example with corfu:

Example with vertico:

The above examples use the following orderless-matching-styles:

(setq orderless-matching-styles
   '(orderless-flex orderless-regexp))

[minad]

Thanks for the proposal. I am a bit skeptical about this addition, since I find it a bit too special. I am unsure if many users will need it, since it hasn't come up in discussion yet, except the linked issue. One can always write a custom splitting function if really needed. Can you show a real use case where we need this? In Corfu and in minibuffer completion in general the space separator works well.
@oantolin What do you think?

[minad]

It seems @oantolin had already rejected this feature request in #102 (comment). I think this still holds without further evidence.