Add Clang 19 to CI test matrices #680

Job	Run time
build (LLVM-Clang-16, Headers, Debug)	1m 22s
build (LLVM-Clang-16, Headers, Release)	1m 24s
build (LLVM-Clang-17, Headers, Debug)	1m 35s
build (LLVM-Clang-17, Headers, Release)	1m 49s
build (LLVM-Clang-17, Module, Debug)	1m 9s
build (LLVM-Clang-17, Module, Release)	1m 32s
build (LLVM-Clang-18, Headers, Debug)	1m 38s
build (LLVM-Clang-18, Headers, Release)	1m 45s
build (LLVM-Clang-18, Module, Debug)	2m 4s
build (LLVM-Clang-18, Module, Release)	1m 36s
build (LLVM-Clang-19, Headers, Debug)	1m 36s
build (LLVM-Clang-19, Headers, Release)	1m 15s
build (LLVM-Clang-19, Module, Debug)	1m 28s
build (LLVM-Clang-19, Module, Release)	1m 14s
	21m 27s

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