Require C++17, port from deprecated qAsConst to std::as_const #106

Job	Run time
build (ubuntu-22.04, Debug, static, 5.15)	5m 1s
build (ubuntu-22.04, Debug, static, 6.5.*)	7m 57s
build (ubuntu-22.04, Debug, shared, 5.15)	4m 25s
build (ubuntu-22.04, Debug, shared, 6.5.*)	5m 53s
build (ubuntu-22.04, Release, static, 5.15)	4m 1s
build (ubuntu-22.04, Release, static, 6.5.*)	2m 9s
build (ubuntu-22.04, Release, shared, 5.15)	1m 52s
build (ubuntu-22.04, Release, shared, 6.5.*)	2m 29s
build (windows-2022, Debug, static, 5.15)	15m 54s
build (windows-2022, Debug, static, 6.5.*)	17m 42s
build (windows-2022, Debug, shared, 5.15)	15m 36s
build (windows-2022, Debug, shared, 6.5.*)	17m 26s
build (windows-2022, Release, static, 5.15)	2m 13s
build (windows-2022, Release, static, 6.5.*)	5m 26s
build (windows-2022, Release, shared, 5.15)	4m 43s
build (windows-2022, Release, shared, 6.5.*)	3m 17s
build (macos-12, Debug, static, 5.15)	3m 54s
build (macos-12, Debug, static, 6.5.*)	7m 24s
build (macos-12, Debug, shared, 5.15)	4m 44s
build (macos-12, Debug, shared, 6.5.*)	5m 28s
build (macos-12, Release, static, 5.15)	1m 29s
build (macos-12, Release, static, 6.5.*)	2m 22s
build (macos-12, Release, shared, 5.15)	4m 3s
build (macos-12, Release, shared, 6.5.*)	1m 39s
	2h 27m 7s

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