Remove unused sounds, put prototype & test sounds in separate directory

[jbphet]

@zepumph was recently doing some work on adding a common UI sound, and pointed out that it's a little confusing when looking at the sounds directory in tambo because there are a lot of sounds, many of which have names that make them sound like they are being used for prototyping and/or testing. This makes it difficult to figure out which ones are eligible for inclusion in a simulation, which should be avoided, and what a newly added sound should be named.

Based on this conversation, I think I should reorganize this directory to have a subdirectory for the prototype and test sounds and have only vetted, reusable sounds at the main level of the directory. I should also remove any of these sounds that are not being used.

[jbphet]

I should address this before doing the tambo portion of phetsims/chipper#1177, since it will save some effort.

[jbphet]

I took a first step on this today where I removed all the sound files that were used for comparing encodings and also removed all unused sounds. I'm thinking that the next step will be to add a subdirectory where the sounds should go that are being used only for testing and demonstration, and leave the vetted, reusable sounds in the top sounds directory. After that, I'll do the rename of the media files, and this should be good to go.

[jbphet]

This is now done, closing.