[Input Dialog refactor] Replace 5 function parameters with 2

[ntrel]

dialogs_show_input_full had grown into a monster taking 2 different sets of callbacks.
The complexity can be removed if:

• the caller creates the combo/entry widget, as they can then connect any special signals to it themselves.
• the caller chooses whether to call gtk_dialog_run

I was also tempted to remove the callback for dialogs_show_input_persistent, but I haven't done that here.

[elextr]

Agree its a better idea to put the common parts in the shared function and the different parts in the callers.

Not tested but LGBI.