Re-order sound-related code (#12382)

Re-order sound-related code (#12382)

Dropped ServerSoundParams -> moved to ServerPlayingSound. This gets rid of the duplicated
'fade' and 'pitch' values on server-side where only one was used anyway.
SimpleSoundSpec is the basic sound without positional information, hence 'loop' is included.

Recursively added PROTOCOL_VERSION to most functions to reduce the versioning mess in the
future. Per-type version numbers are kept for now as a safety rope in a special case.