Add missing header guards.

[AshkanAliabadi]

Stack from ghstack:

• Vulkan caching memory allocator. #42274 Vulkan caching memory allocator.
• Vulkan (source and binary) shader and shader layout cache. #42325 Abstract GLSL source and SPIRV binary shaders in one common construct.
• Refactor Vulkan context into its own files. Use RAII. #42273 Refactor Vulkan context into its own files. Use RAII.
• Const-correctness, variable initialization, and error checking. #42124 Const-correctness, variable initialization, and error checking.
• Add missing header guards. #42272 Add missing header guards.
• Add Vulkan Test to ATen Mobile Tests. #42123 Add Vulkan Test to ATen Mobile Tests.
• Disable validation layers in non-debug builds. #42122 Disable validation layers in non-debug builds.

Differential Revision: D22835546

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@AshkanAliabadi merged this pull request in d0ed1e3.