Improve support for iOS App Store rules by using Xcode-built dynamic XCFramework.

[billhollings]

Apple's iOS App Store does not permit an app to link to naked dylibs. Instead, these must be placed in frameworks, which are embedded in a dynamic version of MoltenVK.xcframework.

• Use Xcode to directly generate a MoltenVK.framework for each platform, and remove create_dylib*.sh scripts.
• Move static XCFramework, containing libMoltenVK.a static libraries, to Package/Latest/MoltenVK/static/MoltenVK.xcframework.
• Generate dynamic XCFramework, containing MoltenVK.framework dynamic libraries, in Package/Latest/MoltenVK/dynamic/MoltenVK.xcframework.
• Add macro MVK_VERSION_STRING to create version string at compile time, use it to validate the CURRENT_PROJECT_VERSION build setting at compile time, and use it at runtime instead of mvkGetMoltenVKVersionString() function.
• Add -w to OTHER_LDFLAGS to dynamic framework builds to suppress spurious linker warnings of the type ld: warning: no platform load command found in '...', assuming: iOS issued from the new linker introduced in Xcode 15.
• Add MoltenVK-MacCat Xcode target and MoltenVK Package (MacCat only) Xcode scheme to avoid building dynamic MoltenVK.framework for the Mac Catalyst platform, because Xcode does not support doing so.
• Always run MoltenVK build scripts, to ensure all components are added to the XCFrameworks, and MoltenVK/Package is always refreshed, even if code compilation is not required.
• Cube demo link to dynamic MoltenVK.framework through dynamic/MoltenVK.xcframework, instead of to naked libMoltenVK.dylib.
• Update the version of Volk used by the Cube demo, to support loading MoltenVK from dynamic frameworks inside Volk.
• Update README.md and MoltenVK_Runtime_UserGuide.md documents.
• Update MVK_PRIVATE_API_VERSION to 40.
• Fix make install to install /usr/local/lib/libMoltenVK.dylib on macOS (unrelated).
• Remove unused MTLAttributeStrideStatic declaration prior to Xcode 15 (unrelated).

This PR replaces #2166.

[billhollings]

@richard-lunarg

This PR replaces #2166. This PR builds dynamic frameworks directly from Xcode, rather than from a script. Doing so improves efficiencies and stability, and allows tvOS Simulator to be supported with a dynamic framework.