introduced Function::print_tree_json #1428

Job	Run time
macos-latest: clang++ Release Threads	30m 52s
macos-latest: clang++ Release OneTBB	3m 38s
macos-latest: clang++ Release PaRSEC	4m 53s
ubuntu-20.04: /usr/bin/g++-9 Release Threads	43m 46s
ubuntu-20.04: /usr/bin/g++-9 Release OneTBB	2m 35s
ubuntu-20.04: /usr/bin/g++-9 Release PaRSEC	2m 34s
macos-latest: clang++ Debug Threads	40m 24s
macos-latest: clang++ Debug OneTBB	4m 27s
macos-latest: clang++ Debug PaRSEC	4m 27s
ubuntu-20.04: /usr/bin/g++-9 Debug Threads	45m 37s
ubuntu-20.04: /usr/bin/g++-9 Debug OneTBB	3m 9s
ubuntu-20.04: /usr/bin/g++-9 Debug PaRSEC	2m 36s
	3h 8m 58s

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