free: Implement almost all functions of the `free` commands #75

Job	Run time
cargo fmt --all -- --check	16s
cargo clippy -- -D warnings (ubuntu-latest)	20s
Code Coverage (ubuntu-latest, unix)	36s
cargo clippy -- -D warnings (macOS-latest)	28s
Code Coverage (macos-latest, macos)	52s
cargo check (ubuntu-latest)	17s
cargo clippy -- -D warnings (windows-latest)	28s
cargo check (macOS-latest)	29s
Code Coverage (windows-latest, windows)	42s
cargo test (ubuntu-latest)	31s
cargo check (windows-latest)	33s
cargo test (macOS-latest)	42s
cargo test (windows-latest)	37s
	6m 51s

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