Add CHANGELOG.md entry for 5.15.0 (#8517) #336

Job	Run time
check_code_style	20s
check_libraries_manifest	6s
build_linux (Release, ubuntu-20.04)	1h 2m 6s
build_windows (Release, 64, windows-2019)	1h 18m 54s
build_linux (RelWithDebInfo, ubuntu-20.04)	49m 44s
build_macos (Release, x86_64, macos-14)	29m 41s
build_windows (Release, arm64, windows-2019)	49m 15s
check_genwebsitejson	5s
build_linux (Debug, ubuntu-20.04)	1h 0m 35s
build_macos (Release, x86_64, macos-15)	27m 41s
build_macos (Release, arm64, macos-14)	47m 1s
build_macos (Release, arm64, macos-15)	54m 24s
check_source_code (ubuntu-20.04)	6m 11s
build_macos (Debug, x86_64, macos-14)	35m 18s
build_macos (Debug, x86_64, macos-15)	36m 40s
build_macos (Debug, arm64, macos-14)	46m 41s
build_macos (Debug, arm64, macos-15)	49m 11s
test_older_macos (x64, macos-13)	16m 25s
build_universal_macos_artifacts	1m 11s
mergeable	1s
	10h 51m 30s

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