Add search bar for the soundfont player

[yohannd1]

The goal of this PR is to make searching for patches easier in the built-in soundfont player.

With this PR selecting a patch should be made easier, and at least for the first bank you can pretty much do most of it with just the keyboard (e.g. to pick patch "Shamisen", open the dialog, type "Sha", press enter, and you're good to go).
This is quite a bit messy at the moment so bear with me. This is the plan:

• Initial implementation - working search bar, implemented referencing the work done on the effect picker search bar.
• Make sorting on the patch column work properly (it's doing string sorting instead of sorting by the numeric value)
• Remove TODOs I added to the code (fix bugs, remove debugging code)