Add Program Change dropdown to Virtual Keyboard

[BrentBaccala]

This was coded by Claude Sonnet 4, running in Windsurf, using the following prompt:

Ardour has a virtual keyboard with an upper row of controls that starts "channel", then "pitchbend", then "modulation", then 4 continous controllers, then "octave", then a few more controls. I want you to add a new control called "Program" just to the left of "Octave". "Program" should be a dropdown (like "Octave"), with 128 choices from 0 to 127. When one of these is selected, the corresponding MIDI Program Change message should be sent on the current channel.

I tested and reviewed the AI's code. It looks fine; I accepted it without any changes other than adding copyright messages.

[x42]

I intentionally did not add a patch-change selector to the MIDI keyboard.

Ardour has dedicated bank/patch selector, which not only lists the program by name, but also include bank select.
The bank/patch selector is also updated to reflect the current program.

[BrentBaccala]

@x42, I see. Didn't know about that feature.

I'm using the virtual keyboard to test Ardour's handling of program change messages coming in from a controller. I don't see any way to route patch selects on a track to Ardour's control surface bindings, which is my new way of doing this, since it doesn't look like a plugin is going to cut it (as we've discussed on another PR).

I'm not sure if sending Program Changes from the virtual keyboard would be useful for anybody but me.

[x42]

I'm using the virtual keyboard to test Ardour's handling of program change messages coming in from a controller.

I see, and yes, short of an actual keyboard that is indeed a good use-case.