Add additional absolute threshold

[chevdor]

Currently, we can set a threashold in %. Let's consider some examples using time below.

Say we have 2 changes:

• Pallet A / Call C1: 100ms -> 200ms <== Here is the big change
• Pallet A / Call C2: 100ms -> 105ms
  The current % change threshold allows focusing on the big change.

If we consider however:

• Pallet A / Call C1: 1µs -> 2µs
• Pallet A / Call C2: 100ms -> 105ms <== Here is the big change

We see that the interesing changes are no longer the big %.

We could address that will a new threshold (in addition to the existing) and allow filtering out all calls under 10µs for instance.