validate-extension

1. Check that we were told which Vulkan extension we are supposed to check. If this was not specified, ask. 2. Download the extension text from `https://docs.vulkan.org/refpages/latest/refpages/source/<extension name>.html` and read it. 3. For each new Vulkan command defined in the given extension, look for its generated implementation named `trace_<name>` in `generated/write_auto.cpp`. Review it for errors, then compare it to the corresponding read function named `retrace_<name>` in `generated/read_auto.cpp`. Verify that the serialized output is likely to be read back in correctly. If not found in generated code, they may have been hardcoded in code in the `src` directory instead. 4. For each new Vulkan structure defined in the given extension, look for its generated implementation named `write_<name>` in `generated/struct_write_auto.cpp`. Review it for errors, then compare it to the corresponding read function named `read_<name>` in `generated/struct_read_auto.cpp`. Verify that the serialized output is likely to be read back in correctly. If not found in generated code, they may have been hardcoded in the `src/hardcode_*.cpp` files instead. 5. Check if any new object types are defined in the given extension. If so, look at the Vulkan creation command for the object type, and see if there is any metadata there we should be tracking. If so, that should be in `src/lavatube.h` under its corresponding `trackable` child class. The trackable class is typically named the same as the object type but in all lower case and its `vk` prefix replaced with `tracked`. 6. Check if the extension has been promoted to core (e.g. "Promotion to Vulkan 1.3"). If it has been promoted, and we have any hardcoded functions, check if these also have core equivalents (ie function name without the extension suffix). Warn if these are missing. Check also if there are hardcoded core functions that are missing extension variants. 7. If the extension adds support for any new SPIRV opcodes, check if these are handled by the spirv-simulator in `external/spirv-simulator/framework/spirv_simulator.cpp`. 8. Check if there are any tests in either our `tests` directory or in `external/tracetooltests` that use this extension. Make a short note if no tests were found.