History of unpack 2 changes

In crates/flow/src/checkpoint.rs, lines 109–164 on a63d3dcd2aef17c39abbf51f2692a4b4c16a8b737a4e18149cc52afd178b7657. 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.