Add EIP: Add blob schedule to EL config files

[lightclient]

Adds a new object to the EL genesis chain config:

of the shape:

"blobSchedule": {
  "prague": { "target": 6, "max": 9 },
  "osaka":   { "target": 12, "max": 16},
  ...
}

[eth-bot]

File EIPS/eip-7840.md

Requires 1 more reviewers from @g11tech, @SamWilsn

[github-actions]

The commit 16a6427 (as a parent of 6586687) contains errors.
Please inspect the Run Summary for details.

[g11tech]

<-- TODO --> tag for tracking via bot

[g11tech]

<-- TODO --> tag

[MarekM25]

Nethermind team is okay with this change. Signaling support 👍

[siladu]

Besu is ok with this change to get us through Prague and have a prototype implementation ready hyperledger/besu#8042

[marioevz]

I prototyped the test changes required in this PR: ethereum/execution-spec-tests#1040

Feedback is appreciated.