Support v1 monitors on MacOS with Metal

[MayaViolet]

Fix for #180 Issue was closed due to monitors being fixed on Metal in v2, but until v2 is declared stable it's useful to have working monitors in v1.

Summary:

• Modified monitor compute shaders & controllers to support variable threadgroup size
• Reduced monitor threadgroup size on Metal to stay under threadgroup size limit
• Changed monitor target shader level & compatibility check to 4.5 since systems that support compute but not full 5.0 still support the monitors' shaders