L2 Cancun support, activate on Ecotone

[protolambda]

Description

Changes:

• explicitly disable Blob transactions
• explicitly change signer methods to use London signer instead of Cancun signer
• activate Cancun when Ecotone superchain fork is set
• update superchain-registry dep (for Ecotone rename)

Tests

To be tested in op-e2e. Draft PR for now.

Metadata

Part of https://github.com/ethereum-optimism/optimism/issues/8701

[protolambda]

Rebased, resolved go.mod conflict, ready to go.