Text Picking

[bytemunch]

What problem does this solve or what need does it fill?

Text should be pickable, with an eye to implementing a first party editable text field.

What solution would you like?

A picking backend for Text and Text2d that gives the position in text of the pointer interaction.

What alternative(s) have you considered?

Third party crates, like bevy_cosmic_edit and bevy_simple_text_input. Though both crates could benefit from having text picking built in.

Additional context

I'm working on a backend in this draft PR, comments and improvements welcome :) #17775

[rparrett]

Related: #17748