Query builder cannot express common queries

[desa]

Related #15545

1. See Query Builder: Add ability to group by columns #15984

2. Get last value across all series for a time range

More of less the query we want to express is

from(bucket: "telegraf")
  |> range(start: v.timeRangeStart, stop: v.timeRangeStop)
  |> filter(fn: (r) => r._measurement == "disk")
  |> filter(fn: (r) => r._field == "used_percent")
  |> last()
  |> group()

[desa]

@r1ckbrown cc

[desa]

Plan is to add special functions to functions window.

[hoorayimhelping]

related: #16076

[kristinarobinson]

Will solve with flows.