feat(core): add `Manager::unmanage` #11426

Job	Run time
test (x86_64-pc-windows-msvc, windows-latest, 1.71.0, false, test, --no-default-features, no-defa...	5m 13s
test (x86_64-pc-windows-msvc, windows-latest, 1.71.0, false, test, --all-features, all)	6m 35s
test (x86_64-unknown-linux-gnu, ubuntu-latest, 1.71.0, false, test, --no-default-features, no-def...	4m 46s
test (x86_64-unknown-linux-gnu, ubuntu-latest, 1.71.0, false, test, --all-features, all)	7m 34s
test (aarch64-apple-darwin, macos-14, 1.71.0, false, test, --no-default-features, no-default)	2m 2s
test (aarch64-apple-darwin, macos-14, 1.71.0, false, test, --all-features, all)	2m 50s
test (aarch64-apple-ios, macos-latest, 1.71.0, false, build, --no-default-features, no-default)	1m 5s
test (aarch64-apple-ios, macos-latest, 1.71.0, false, build, --all-features, all)	2m 8s
test (aarch64-linux-android, ubuntu-latest, 1.71.0, true, build, --no-default-features, no-default)	1m 17s
test (aarch64-linux-android, ubuntu-latest, 1.71.0, true, build, --all-features, all)	1m 35s
	35m 5s

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