bump clang-format to clang-15 #10784

Job	Run time
check-ubuntu-20_04-make-clang-smt-z3	5m 24s
check-ubuntu-20_04-make-gcc	18m 39s
check-ubuntu-20_04-cmake-gcc	17m 0s
check-ubuntu-20_04-cmake-gcc-KNOWNBUG	3m 17s
check-ubuntu-20_04-cmake-gcc-THOROUGH	9m 52s
check-ubuntu-20_04-make-clang	24m 6s
check-ubuntu-22_04-cmake-gcc	15m 3s
check-ubuntu-22_04-cmake-gcc-32bit	15m 41s
check-ubuntu-22_04-make-clang	17m 19s
check-ubuntu-24_04-cmake-gcc-14	16m 16s
check-macos-13-make-clang	55m 0s
check-docker-image	21m 31s
check-macos-14-cmake-clang	1h 35m 28s
check-string-table	2m 12s
check-vs-2019-cmake-build-and-test	33m 20s
check-vs-2022-make-build-and-test	18m 46s
include-what-you-use	23m 20s
windows-msi-package	5m 55s
	6h 38m 9s

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