InitialDynoStats used to be assigned inside `runAllPasses`, but the
assignment executed before any of the passes. As we've moved
`EstimateEdgeCounts` into a pass out of ProfileReader, it needs to
execute before initial dyno stats are set.
Thus move `InitialDynoStats` into BinaryContext and assignment into
`DynoStatsSetPass`.
a38f0157f2