Add extra metadata to metadata::Region or Region itself.

[CPerezz]

See: https://github.com/privacy-scaling-explorations/zkevm-circuits/pull/994/files#r1052139018 for more details.

@ed255 description:

Ideally, given an impl Circuit loaded with witness data, we would obtain a list of regions with medatada. This metadata would be the list of columns used in the region, and for each column, the range of rows assigned.

[ed255]

Ideally, given an impl Circuit loaded with witness data, we would obtain a list of regions with medatada. This metadata would be the list of columns used in the region, and for each column, the range of rows assigned.

[CPerezz]

I like it!
We already picked up tasks for this week's sprint. But will definitely purpose it for the next one!

[davidnevadoc]

I think the issue is not quite solved. The new functions allow to access some extra information from the MockProver but nothing else.
This is really helpful to check for bugs like the witness-dependent sized circuits but it doesn't give us extra info in configure time (which is what we need to solve privacy-scaling-explorations/zkevm-circuits#1028 )

[davidnevadoc]

Any thoughts on this @CPerezz @ed255 ?

[CPerezz]

We could have a quick chat to revisit the problem.
But I'm not sure this is still a concern (or a big prio at least).

[davidnevadoc]

I'd agree that we are not in a hurry. However it would be nice to solve as it is blocking this other issue privacy-scaling-explorations/zkevm-circuits#1028

[CPerezz]

That's right! @ed255 should we bring it to this week's agenda??

[ed255]

That's right! @ed255 should we bring it to this week's agenda??

Sounds good to me!