brittle parsing of outputs response

[grobian]

https://github.com/Difegue/MpcNET/blob/ddd090c6d0ccd116696043c8b32b44a831f148e8/Sources/MpcNET/Commands/Output/OutputsCommand.cs#L38C86-L38C87

This assumes MPD server will emit 4 lines (excluding attributes) for all outputs. This may change, or just be different on other implementations (such as owntone's MPD: https://github.com/owntone/owntone-server/blob/master/src/mpd.c#L3797-L3807).

In the future MPD might add (or remove) keys here, and perhaps it is safer to run through all lines and use outputid as marker for a new output instead of assuming it's once very 4 lines.

(I've got a PR to rectify owntone's output for the moment in owntone/owntone-server#1804)