musics: Fill in remaining FreeDM music slots.

Reuse music from phase 2 as music for the remaining FreeDM levels
that are still missing music.
musics: Use dave3d20.mid for D_READ_M.

Ditch the current D_READ_M, which is awful and frankly, annoying.
Use Jute's dave3d20.mid instead which seems to fit the purpose
much better, and change D_DM22 to use a different Jute track, as
it was using dave3d20.mid.