Add unit test ValueMetricProducer on boundary

Mostly to add test to assure the corner cases are covered.
One minor logic change is if two true conditions happen, in the case
when following happen:
(bucket boundary1) -> (condition false) -> (condition true) -> (pull
triggered for the boundary1)
Previously we take the latest. Now we skip the late boundary pull.

Bug: 76384731
Test: unit test
Change-Id: I345c2210a58bf03eb91d65742573073d2668358b