mac-videotoolbox: Add Spatial AQ option (macOS 15)

[dsaedtler]

Description

Adds support for the new spatial aq property introduced in macOS 15: https://developer.apple.com/documentation/videotoolbox/kvtcompressionpropertykey_spatialadaptiveqplevel?language=objc

Motivation and Context

Disabling spatial aq seems to improve video quality of screen content (such as games) by a decent bit.

How Has This Been Tested?

M1 Pro with FFmpeg patch applied for direct frame-accurate comparison of AOM video game compression test corpus.

Types of changes

• New feature (non-breaking change which adds functionality)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.

[dsaedtler]

Apparently we need Xcdoe 16 for this to work, which is getting removed from the macos-14 images soon (actions/runner-images#10703) so we'd have to update to macos-15. Let's see what breaks?

[Lain-B]

I'm not a macOS specialist so might want @PatTheMav to give this a look just as a double-check, but seems trivial/simple enough so I threw an approval on it.

[PatTheMav]

If this does indeed add a requirement to use Xcode 16 (which is fine in my book), then the lower version boundaries should be changed here as well:

obs-studio/cmake/macos/compilerconfig.cmake

Lines 24 to 25 in 52a0486

	set(_obs_macos_minimum_sdk 14.2) # Keep in sync with Xcode
	set(_obs_macos_minimum_xcode 15.1) # Keep in sync with SDK