Refactor public MVKDevice content into MVKDeviceTrackingMixin functions.

[billhollings]

This is a non-functional code-maintenance change.

Previously, MVKDevice contained a significant amount of publicly exposed internal content. This patch adds functions to MVKDeviceTrackingMixin to better encapsulate, consolidate & streamline access to this content.

• Make MVKDeviceTrackingMixin a friend of MVKDevice & MVKPhysicalDevice.
• Hide public MVKDevice content behind MVKDeviceTrackingMixin functions.
• Remove similar MVKDevice content pointers from MVKCommandEncoder.
• MVKDevice remove getPhysicalDevice(), getPixelFormats() & getMTLDevice(), to focus access through MVKDeviceTrackingMixin.
• Move performance tracking functions to MVKDeviceTrackingMixin to remove need to reference MVKDevice multiple times when marking performance values.
• Subclass MVKQueueSubmission, MVKMetalCompiler, MVKShaderLibrary, and MVKShaderLibraryCache from MVKBaseDeviceObject to make use of these changes.

Note to reviewers:

• This is a non-functional change and passes the same CTS tests as previously.
• The primary design changes of interest are in the declarations of MVKDeviceTrackingMixin and MVKDevice in MVKDevice.h, and to MVKCommandEncoder in MVKCommandBuffer.h.
• The remaining changes are simple find-and-replace syntax changes to delegate to MVKDeviceTrackingMixin instead of reaching into MVKDevice.

[billhollings]

Sorry about that. Took me a while to get through this massive refactoring.

No apology needed. And thanks.

I wrote the Note to reviewers above so you could skip all the search & replace noise. But I appreciate your epic diligence and accuracy once again! 👍🏻