ui: when zooming in on 30m downsampled data metrics page shows empty charts

**Describe the problem**

When inspecting a tsdump-loaded data chunk that's been downsampled to 30m intervals, the metrics are only visible in the DB Console when we're zoomed out to week+ periods even though when scrubbing the data it's clear there's more detail. Zooming in shows empty charts.

**To Reproduce**

Load up a tsdump with downsampled data, navigate to 1m or 1w view in Metrics page, observe data. Zoom by dragging a selection on the chart and observe the empty graphs.

**Expected behavior**
Charts should zoom, with reduced resolution of points as expected

**Additional data / screenshots**
This can be mitigated by overriding the lookup table in https://github.com/cockroachdb/cockroach/blob/master/pkg/ui/workspaces/cluster-ui/src/timeScaleDropdown/utils.ts#L14-L60 to use the 30m interval at all timescales. Then the zoom works. We need to have more intelligence about the timescales we're requesting from the backend in these scenarios.

I haven't done enough digging into the tsdb code to see if any changes are necessary there. It seems like we should always request data at 10s intervals from the backend and it will adjust if lower resolution is all that's availab.e

**Environment:**
- CockroachDB version: All versions are affected
- Client app: DB Console

Jira issue: CRDB-54545