Only include context observer block when workgroup types available.

This allows real-time threads to join an audio workgroup on Apple platforms.

Using a preferred channel config with no input or output channels could
cause an assertion here because the AudioProcessor will always have a
single input/output bus by default.

AudioProcessorParameterWithID pre-dates HostedAudioProcessorParameter,
which is why AudioProcessorParameterWithID was initially used for this
purpose.

This comparison can break when relaxing IEEE compliance and enabling
full optimisations.

On some platforms, the superclass implementation can throw if it detects
that the preset data is malformed, but it's not clear exactly how the
system determines this.

We now apply only the JUCE state.

JUCE no longer depends on built artifacts of the AAX_SDK