This has mainly performance benefits, so that we only need to call into
all processors once for every audio buffer segment. It requires
adjusting quite some logic in most processors and in Track, as we have
to consider a larger collection of notes and samples at each step.
There's some cautionary TODOs in the currently unused LibDSP tracks
because they don't do things properly yet.
* Don't inherit from Core::Object everywhere, that's overkill. Use
RefCounted instead.
* Change some constructor visibilites to facilitate the above.
* default-implement all virtual destructors if possible.
* Drive-by include hygiene.
SonarCloud flagged this as m_delay_buffer is technically uninitialized
at the point at which the POD types are initialized in a constructor.
I don't check to see if this was actually a real issue, as the member
is ultimately unused. So lets just get rid of it.
