Support compare view

[shawncao]

This is an end to end feature request to show data in a diff view. Including

Table
Timeline
Bar / line
Flame (🔥 )

I think there are two major comparison types we should support, and this will simplify how diff is defined and supported in Nebula.

• Diff on two different time range. In this mode, we allow user to input two different time ranges, and the rest of the data/metrics are the same. In some visualization, we may want to introduce T1 vs T2 as dimensions for diff view.

• Diff on two different filter set. (time range is essentially one specific filter) Here, we generate two types T1 and T2 to represent two different filters, and the result will be presented in two groups for comparison.