Allow rebinding of text object selection keys (and show a dialog list)

[eugenesvk]

Currently object selections like select_textobject_inner seem to have hardcoded keybinds for the supported objects like w word, f function, c class etc.

Since in my keybindings w isn't tied to a word, I'd also like to be able to change these internal keybindings as well to match my word-based keybinds from the Normal mode

I think it'd be great if there were a way to use Helix dialog popup list for this as well since currently select_textobject_inner doesn't show any hints unlike some other minor modes that do show the the full list of available keybinds