meson: major simplification to build definition of satellites

This is a major improvement to the build definition of satellites and avoids the stupid copy-and-paste. Should have read the docs earlier, but essentially instead of using macros, meson recommends iterating over a list / dictionary. This is exactly what this MR does: in the meson.build for each satellite, one now only defines the type, sources and dependencies. This is added to a list, over which we iterate to do the exact same thing every time.

Also disables the DevNullReceiver and RandomTransmitter satellites again and fixes their docs.