On macos, if an app enables multisampling with 2x, it crashes if the device does not support this sample count

For example, the attached project (an empty ApplicationWindow) crashes when it runs on a Macbook Pro 13 (mid-2014, MacbookPro11,1) with an Intel Iris graphic card

-[MTLTextureDescriptorInternal validateWithDevice:]:1248: failed assertion `Texture Descriptor Validation
MTLTextureDescriptor sampleCount (2) is not supported by device.

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Thread 8 Crashed:: QSGRenderThread
0 libsystem_kernel.dylib 0x00007fff204b5462 __pthread_kill + 10
1 libsystem_pthread.dylib 0x00007fff204e3610 pthread_kill + 263
2 libsystem_c.dylib 0x00007fff20436720 abort + 120
3 libsystem_c.dylib 0x00007fff204359d6 __assert_rtn + 314
4 com.apple.Metal 0x00007fff28567fe4 MTLReportFailure.cold.1 + 43
5 com.apple.Metal 0x00007fff285561b2 MTLReportFailure + 538
6 com.apple.Metal 0x00007fff2854ff6a _MTLMessageContextEnd + 987
7 com.apple.Metal 0x00007fff284b8151 -[MTLTextureDescriptorInternal validateWithDevice:] + 2220
8 com.apple.driver.AppleIntelHD5000GraphicsMTLDriver 0x00007fff62c5a976 validateTextureDescriptor(MTLTextureDescriptor*, id<MTLBuffer>, MTLIGAccelDevice*) + 81
9 com.apple.driver.AppleIntelHD5000GraphicsMTLDriver 0x00007fff62c5b949 -[MTLIGAccelDevice newTextureWithDescriptor:] + 41
10 org.qt-project.QtGui 0x0000000108ad76ee 0x108629000 + 4908782
11 org.qt-project.QtGui 0x0000000108ade3b1 0x108629000 + 4936625
12 org.qt-project.QtQuick 0x00000001060c29d2 0x105e00000 + 2894290
13 org.qt-project.QtQuick 0x00000001060c3b51 0x105e00000 + 2898769
14 org.qt-project.QtCore 0x00000001097376a8 0x10950c000 + 2274984
15 libsystem_pthread.dylib 0x00007fff204e3950 _pthread_start + 224
16 libsystem_pthread.dylib 0x00007fff204df47b thread_start + 15

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Metal supports 1x and 4x on all devices. 2xand 8x are only supported on some devices (see https://developer.apple.com/documentation/metal/mtldevice/1433355-supportstexturesamplecount?language=objc)

QRhiMetal should check if a device can support the given sample count by calling supportsTextureSampleCount