vm.Synth was used only in a few places, reduce the number of
exported functions. Also, if we ever add some global configuration
to GoSynther e.g. samplerate, we have a mechanism to do so, instead
of the Synth function.
The Render name misleading as it did not do the same thing as normal
Synth.Render, because it disregarded time limits. Conceptually, as
the function modifies the state of the synth, it would be better to
be synth.Fill(audioBuffer), but we cannot define methods on
interfaces; therefore, it is audioBuffer.Fill(synth) now.
The VMs now release all envelopes by default, so this mechanism was
useless / did not actually start them as unreleased even when you
thought they did.
The -er suffix is more idiomatic for single method interfaces, and
the interface is not doing much more than converting the patch to a
synth. Names were updated throughout the project to reflect this
change. In particular, the "Service" in SynthService was not telling
anything helpful.
