Missing public/exported docstrings

[christiangnrd]

Found using Docs.undocumented_names from 1.11.
They should also be added to the documentation when a docstring is created.

Metal

• Metal
• is_managed
• is_private
• is_shared
• device
• MtlMatrix
• MtlVecOrMat
• MtlVector
• MetalBackend
• MtlDeviceMatrix
• MtlDeviceVector
• MTL
• MPS

MTL

Important:

• Managed
• Private
• Shared
• CPUStorage

Other:

• air_support
• air_version
• is_m1
• is_m2
• is_m3
• macos_version
• metal_support
• metal_version
• metallib_support
• darwin_version
• supports_family
• add_functions!
• append_current_function!
• commit!
• dispatchThreadgroups!
• endEncoding!
• set_buffer!
• set_function!
• supports_destination
• MTLBinaryArchive
• MTLBinaryArchiveDescriptor
• MTLBuffer
• MTLCompileOptions
• MTLComputeCommandEncoder
• MTLComputePipelineDescriptor
• MTLComputePipelineState
• MTLCreateSystemDefaultDevice
• MTLEvent
• MTLFence
• MTLFunction
• MTLFunctionDescriptor
• MTLHeap
• MTLHeapDescriptor
• MTLLibrary
• MTLLibraryFromData
• MTLLibraryFromFile
• MTLOrigin
• MTLRegion
• MTLSharedEvent
• MTLSharedEventHandle
• MTLSize
• MTLTexture
• MTLTextureDescriptor
• MTLCommandBuffer
• MTLCommandBufferDescriptor
• MTLCommandQueue
• ReadUsage
• ReadWriteUsage
• WriteUsage
• MTLResource
• MTLBlitCommandEncoder
• append_copy!
• append_fillbuffer!
• append_sync!

Unexport:

• @sv_str
• SimpleVersion
• AS

[maleadt]

I guess we should first focus on documenting Metal, before moving to MTL/MPS which aren't likely to be imported or even used by users directly. For these modules, the documentation would likely be a copy of Apple's documentation anyway (which is similarly why many of these aren't thoroughly documented in CUDA.jl).

A couple should also be unexported: SimpleVersion/@sv_str definitely, and AS probably too.