Enable PoV weight reclaim in Staking+EPMB

[kianenigma]

I have made this PR ready last year as a follow-up to #9925, but separate it into a different PR for easier review.

The recent issue in Paseo in #11034 promoted me to revive it. This PR does two things:

1. It adds the ability to papi-test of e2e staking+election tests to draw the diagram of all weights consumed
2. It updates the on_poll hook of both pallets to use the weight reclaim.

Below is the weight diagram (left without refund, right with refund). As you see, in both the snapshot and export phase we see a meaningful reduction in the onchain weight.

Note: This PR clearly shows that some process is consuming around 600k PoV on all blocks. You can also see this if you open any random block in PAH in subscan.

[michalkucharczyk]

Below is the weight diagram (left without refund, right with refund). As you see, in both the snapshot and export phase we see a meaningful reduction in the onchain weight.

The Y axis range differs on both graphs, making it difficult to compare.
What is "snapshot" and "export" phase - what block range?

[kianenigma]

Below is the weight diagram (left without refund, right with refund). As you see, in both the snapshot and export phase we see a meaningful reduction in the onchain weight.

The Y axis range differs on both graphs, making it difficult to compare. What is "snapshot" and "export" phase - what block range?

I will try and plot them on the same chart next, though if you see the numbers, it will become clearer. The snapshot is the first part, and the export is the last part where we see a difference in the two charts.

I will share a full export HTML with charts soon to clarify.