Relabel Custom date range to Custom time interval in time picker and update tooltips #84361
Description
According to #83420 we prefer the term time interval instead of date range. Therefore the final option in the time picker should be relabeled to Custom time interval.
Consider changing the previous and next tooltips from previous/next timeframe to previous/next time interval
Add a tooltip to the Now button that is explanatory and doesn't repeat the button label.
Jira issue: CRDB-17616