Add license reporting and "vcpkg license-report" command. #1971

Job	Run time
json-schema	1m 4s
format	4m 1s
builds / build (windows-2022, windows-ci)	2h 0m 1s
builds / build (ubuntu-20.04, linux-ci)	3m 41s
builds / build (macos-13, macos-ci)	2m 19s
	2h 11m 6s

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