Rename c++ header files to `*.hpp` #6

Job	Run time
build (linux, single, x86_64, template_debug, ubuntu-20.04)	7m 7s
build (windows, single, x86_32, template_debug, windows-latest)	3m 30s
build (windows, single, x86_64, template_debug, windows-latest)	3m 40s
build (macos, single, universal, template_debug, macos-latest)	7m 58s
build (android, single, arm64, template_debug, ubuntu-20.04)	9m 37s
build (android, single, arm32, template_debug, ubuntu-20.04)	9m 23s
build (android, single, x86_64, template_debug, ubuntu-20.04)	7m 40s
build (android, single, x86_32, template_debug, ubuntu-20.04)	6m 21s
build (ios, single, arm64, template_debug, macos-latest)	4m 22s
build (web, single, wasm32, template_debug, ubuntu-20.04)	11m 7s
build (linux, single, x86_64, template_release, ubuntu-20.04)	7m 39s
build (linux, double, x86_64, template_debug, ubuntu-20.04)	7m 54s
build (windows, double, x86_32, template_debug, windows-latest)	4m 5s
build (windows, double, x86_64, template_debug, windows-latest)	4m 25s
build (macos, double, universal, template_debug, macos-latest)	8m 29s
build (android, double, arm64, template_debug, ubuntu-20.04)	7m 29s
build (android, double, arm32, template_debug, ubuntu-20.04)	7m 32s
build (android, double, x86_64, template_debug, ubuntu-20.04)	10m 47s
build (android, double, x86_32, template_debug, ubuntu-20.04)	7m 27s
build (ios, double, arm64, template_debug, macos-latest)	4m 35s
build (web, double, wasm32, template_debug, ubuntu-20.04)	11m 13s
build (linux, double, x86_64, template_release, ubuntu-20.04)	7m 34s
merge	0s
	2h 39m 54s

Provide feedback