[all] Dynamic bundle size priced PVG

[dancoombs]

Describe the feature
Currently all PVG calculations assume a bundle size of 1. This requires the user to pay for:

• Intrinsic gas
• Bundle calldata & DA cost
• Shared aggregator cost

The bundler can often create bundles > size 1, and currently has no way of sharing those cost savings with the user.

This feature is around enabling users to take advantage of larger bundles resulting in lower cost

Additional context

High level:

• PVG estimation can be done at different bundle sizes.
  • This is likely the hardest part of the feature, what bundle size should be used? Should the bundler suggest? Should the user choose?
• Precheck should be lenient about the PVG
  • Choose a fixed bundle size to compare to
• Pool eligibility should also be done at a certain bundle size - either fixed or suggested by the builder
• Bundle building algo should include all UOs who have sufficient PVG for the bundle size and current DA costs
  • This is also difficult, what algo should be used here?

On the current signature-aggregator branch a few of the bundle size assumptions are tagged with // TODO(bundle) for quick lookup.