Make Interval class final #1303

Job	Run time
cpp-lib-build (ubuntu-22.04, clang, OFF)	1m 11s
cpp-lib-build (macos-15, clang, ON)	29s
cpp-lib-build (macos-15, gcc, ON)	34s
cpp-lib-build (ubuntu-22.04, gcc, OFF)	46s
cpp-lib-build (ubuntu-22.04, clang, ON)	1m 5s
cpp-lib-build (windows-2022, clang, ON)	25s
cpp-lib-build (macos-15, clang, OFF)	32s
cpp-lib-build (macos-15, gcc, OFF)	39s
cpp-lib-build (ubuntu-22.04, gcc, ON)	43s
cpp-lib-build (windows-2022, clang, OFF)	1m 2s
cpp-lib-build (windows-2022, cl)	24s
build (macos-15, cpp)	21s
build (macos-15, go)	9s
build (macos-15, tool)	1s
build (macos-15, dart)	11s
build (macos-15, javascript)	1m 15s
build (macos-15, php)	58s
build (macos-15, java)	17s
build (ubuntu-22.04, tool)	1m 11s
build (ubuntu-22.04, cpp)	1m 5s
build (ubuntu-22.04, dart)	1m 14s
build (macos-15, csharp)	1s
build (macos-15, typescript)	1s
build (macos-15, python3)	1s
build (ubuntu-22.04, csharp)	1m 10s
build (ubuntu-22.04, go)	1m 13s
build (ubuntu-22.04, javascript)	1m 19s
build (ubuntu-22.04, java)	1m 1s
build (ubuntu-22.04, typescript)	1m 17s
build (windows-2022, tool)	1s
build (windows-2022, csharp)	59s
build (ubuntu-22.04, python3)	1m 15s
build (ubuntu-22.04, php)	1m 14s
build (windows-2022, go)	1s
build (windows-2022, dart)	1s
build (windows-2022, cpp)	1s
build (windows-2022, javascript)	1s
build (windows-2022, python3)	59s
build (windows-2022, typescript)	1s
build (windows-2022, java)	59s
build (windows-2022, php)	1s
	26m 8s

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