Refactor `unused_finder/logger` into standalone package #366

Job	Run time
health checks	1m 23s
build+test x86_64-unknown-linux-gnu on ubuntu-20.04	5m 44s
build aarch64-unknown-linux-gnu on ubuntu-20.04	2m 35s
build x86_64-apple-darwin on macos-13	5m 31s
build aarch64-apple-darwin on macos-latest	2m 54s
build+test x86_64-pc-windows-msvc on windows-latest	10m 40s
build aarch64-pc-windows-msvc on windows-latest	4m 40s
	33m 27s

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