feat(ethportal-api): add and refactor post-merge header proofs

[ogenev]

What was wrong?

We need types to contain post-merge execution header proofs

How was it fixed?

• move all header proofs to a new header_proofs.rs file inside the execution folder.
• add and update post-merge header proof types
• rename the old header_proofs.rs file in the consensus folder to historical_summaries.rs because now It contains only those types.

Post-merge proof types are based on the following portal specs PRs:

• Add HistoricalRootsBlockProof for merge till capella blocks portal-network-specs#287
• Add HistoricalSummariesBlockProof for headers from Capella onwards portal-network-specs#291

To-Do

• Clean up commit history and use conventional commits.

[njgheorghita]

nitpick I'd probably prefer execution/header_with_proof.rs over execution/header_proofs.rs. It's slightly longer, but the latter makes it sound like the file only contains the proofs rather than the HeaderWithProof type itself along with the proofs