free: Implement almost all functions of the `free` commands #79

Job	Run time
cargo fmt --all -- --check	13s
cargo clippy -- -D warnings (ubuntu-latest)	18s
Code Coverage (ubuntu-latest, unix)	1m 11s
cargo clippy -- -D warnings (macOS-latest)	26s
cargo check (ubuntu-latest)	18s
cargo test (ubuntu-latest)	45s
cargo clippy -- -D warnings (windows-latest)	28s
cargo check (macOS-latest)	45s
Code Coverage (macos-latest, macos)	51s
Code Coverage (windows-latest, windows)	44s
cargo test (macOS-latest)	35s
cargo check (windows-latest)	45s
cargo test (windows-latest)	34s
	7m 53s

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