Now that Suspense retries have their own dedicated set of lanes
(#19287), we can determine if a render includes only retries by checking
if its lanes are a subset of the retry lanes.
Previously we inferred this by checking
`workInProgressRootLatestProcessedEventTime`. If it's not set, that
implies that no updates were processed in the current render, which
implies it must be a Suspense retry. The eventual plan is to get rid of
`workInProgressRootLatestProcessedEventTime` and instead track event
times on the root; this change is one the steps toward that goal.
The relevant tests were originally added in #15769.
Andrew Clark
970fa122d8