History of unpack 2 changes

In crates/flow/src/checkpoint.rs, lines 109–164 on 1215f05ff8d00714f50b88d5038397d318d459ae691ad0c95baa3297dc5e5b68. Every change that wrote or deleted one of these lines, or deleted a line from between them. Exact, because each line keeps its identity across edits; edits elsewhere in the file are not here. Also: oxy log -L 109,164:crates/flow/src/checkpoint.rs.