Previously, the AudioProcessorPlayer would always match the
AudioProcessor's bus configuration to the requested bus configuration,
even if the processor did not explicitly support the requested
configuration.

Now, if the requested configuration has one or fewer input channels, the
AudioProcessorPlayer will attempt to find a multi-input channel layout
for which `checkBusesLayoutSupported` returns true, and will use such a
layout if it exists. Otherwise, as a last resort, it will fall back to
using the channel layout requested by the AudioProcessorPlayer.

If the AudioProcessorPlayer has no input channels, but the wrapped
processor is initialised with multiple input channels, each of these
inputs will be fed with silence.

If the AudioProcessorPlayer has a single input channel, but the wrapped
processor is initialised with multiple input channels, each input
channel will be fed with a copy of the AudioProcessorPlayer's mono
input.

This patch also moves PluginHostType into juce_audio_processors in order
to allow hiding of function implementations.

Reports the correct host name for Apple hosts on M1 which host plugins
in a separate process.

Affected hosts are:
- Logic Pro
- GarageBand
- MainStage
- Final Cut Pro

Live calls getSize() before the plug-in has been attached to the system window and can query the correct system scale factor, this size is then used to resize the plug-in after it has been attached resulting in an unscaled window size.