test-patchbomb: fix the test
With the experimental config `progress.estimate` removed, the progress
output in `test-patchbomb.t` has a minor change: it shows ETA since the
beginning.
(This could be folded into f428c3)
progress: make ETA only consider progress made in the last minute
This patch limits the estimate time interval to roughly the last minute
(configurable by `estimateinterval`) to be more practical. See the test
change for why this is better.
.. feature:: Estimated time is more accurate with non-linear progress
Differential Revision: https://phab.mercurial-scm.org/D820