metal: refactor PrivateCapabilities creation

[jinleili]

Description

• refactor version_at_least, make use like objc @available(macOS xx.x, iOS xx.x, *) to simplify version check logic.

• Follow Apple's API doc:

If your app is running on an operating system that supports the supportsFamily: method, use that method instead.

Some original family_check && supports_family conditons，if MTLGPUFamily lower than Apple6, replaced to:

if family_check { supports_family(xx) } else { supports_feature_set(xx) }

Some original supports_feature_set || (family_check && supports_family) conditons，changed family_check && supports_family to front.

• Follow Apple's Detecting GPU Features doc:

More recent GPUs have higher version numbers and support larger feature sets. A higher GPU version is always a superset of an earlier version in the same GPU family.
...
If a GPU supports a feature set, it supports all features provided by earlier members of the same family, and all features in earlier software revisions. For example, MTLFeatureSet_iOS_GPUFamily4_v2 is version 2 of family 4, so it supports the same features as version 1, as well as all features supported by families 1, 2, and 3.

supports_any does not need to enumerate all feature sets in the same family，It is enough to keep only the first one。

The OS is updated every year, Maybe some day, we can remove all supports_feature_set code.

• format_r32_xx detecting is wrong, all GPU Families supports write, r32_float support filer only on macOS, and M1 Mac also support iOS_GPUFamily_xx feature:

Similarly, format_rg32_xx , format_rgba32_xx, format_depth16unorm_xx, format_bgr10a2_xx need to be fixed too.

• supports_feature_set(iOS_GPUFamily1_v1) is equal to !os_is_mac
• supports_feature_set(macOS_GPUFamily1_v1) is equal to os_is_mac
• supports_any(&[iOS_GPUFamily1_v1, macOS_GPUFamily1_v1]) is equal to true
• !supports_any(&[iOS_GPUFamily1_v1, macOS_GPUFamily1_v1]) is equal to false

Testing
Tested wgpu examples on M1 Mac, Intel Mac.
Tested wgpu-on-app demos on M1 Mac, Intel Mac, iPhone 6 Plus, iPad Mini4, iPhone 12 Pro.
Tested my private app 字习 Pro on M1 Mac, iPhone 6 Plus, iPad Mini4, iPhone 12 Pro，iPad Pro 2018