Insights/record from interval start

Created by: coury-clark

Closes #23516 (closed)

Historical data frames were being calculated by selecting a time at the middle of the frame and trying to find the "nearest" commit. This behavior led to some confusing / unexpected insight charts.

This change makes all historical frames select the start time as the recording time, and will pick the commit which occurred most recently. This way we will always generate a chart with the start of each frame being sampled at the appropriate commit.

This causes the initial data frames to sometimes be quite old if the repo has few updates, but that doesn't actually impact our storage or performance needs.