fix(dashboards): Rebalance chart interval options and defaults

[gggritso]

Rebalance chart interval ladders and default strategy on dashboards to reduce data point counts and improve chart smoothness.

See DAIN-1376 for full context and audit.

tl;dr the current behaviour is: give everyone 3-4 options for the interval, always default to the highest granularity. This causes much jank, since so much data is loading! What we think we want to do is choose the second highest granularity by default, but in many cases that's not enough points.

In this PR I both switch to using the second-highest granularity by default (in Dashboards, not Explore), and also re-balance the options so things are a bit more even. It's a bit of science and a bit of art, but the results should be pretty decent!

Before

Duration Range	1m	5m	15m	30m	1h	3h	12h	1d
1h–6h	60–359	12–71	4–23	-	-	-	-	-
6h–48h	-	72–575	24–191	12–95	6–47	-	-	-
48h–7d	-	-	192–671	96–335	48–167	16–55	-	-
7d–14d	-	-	-	336–671	168–335	56–111	14–27	-
14d–30d	-	-	-	-	336–719	112–239	28–59	14–29
30d–90d	-	-	-	-	-	240–720	60–180	30–90

Defaults (bold) hit 575–720 points at the upper end of every band, which is an awful lot of points to show by default.

After

Duration Range	1m	5m	10m	30m	1h	3h	6h	12h
1h–6h	60–359	12–71	-	-	-	-	-	-
6h–12h	360–719	72–143	36–71	-	-	-	-	-
12h–2d	-	144–575	72–287	24–95	-	-	-	-
2d–4d	-	-	288–575	96–191	48–95	-	-	-
4d–14d	-	-	-	192–671	96–335	32–111	-	-
14d–30d	-	-	-	-	336–719	112–239	56–119	-
30d–90d	-	-	-	-	-	240–720	120–360	60–180

Defaults (bold) stay in the 60–360 range. High granularity is still available for those who want it.

Changes

• Replace 15m with 10m, add 6h, remove 1d from interval options
• Rebalance MINIMUM/MAXIMUM ladders with new thresholds at 12h, 2d, 4d
• Default to second-biggest interval on dashboards (USE_SECOND_BIGGEST), keep Explore using the highest granularity by default
• 1h–6h band naturally defaults to 1m (finest) since it only has 2 options

Refs DAIN-1376

[linear-code]

DAIN-1376 Tune default interval on dashboard pages when selecting time window