History of tiers 5 changes

In crates/flow/src/runner.rs, lines 531–553 on v0.4.0. 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 531,553:crates/flow/src/runner.rs.