History of tiers 3 changes

In crates/flow/src/runner.rs, lines 400–419 on 35f7a849bcc5c0bc72f9fb87eaee2621d13e768475104423896c25865e32f985. 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 400,419:crates/flow/src/runner.rs.