- Add MVKConfiguration::timestampPeriodLowPassAlpha, along with matching
MVK_CONFIG_TIMESTAMP_PERIOD_LOWPASS_ALPHA env var.
- Add MVKConfigMembers.def file to describe MVKConfiguration members,
to support consistent batch handling of members.
- Add env var & build settings MVK_CONFIG_DEBUG, plus legacy
MVK_CONFIG_ALLOW_METAL_EVENTS & MVK_CONFIG_ALLOW_METAL_FENCES.
- Simplify environment variable retrieval functions and macros.
- Rename MVKDevice::updateTimestampsAndPeriod() to updateTimestampPeriod().