PromQL: Convert more native histogram tests to promql-test framework (prometheus#15419)

This converts `TestNativeHistogram_SubOperator` to the promql testing framework. It also removes `TestNativeHistogram_Sum_Count_Add_AvgOperator`, which got converted earlier.

Signed-off-by: Neeraj Gartia <[email protected]>

Author: NeerajGartia21