feat(WIP): Validium pubdata abstraction as enum

[ilitteri]

Description

PoC of Validium mode pubdata abstraction as enum

Changes

• Add PubdataStorageMode enum with Validium and Rollup variants.
• Add pubdata_storage_mode field to SenderConfig.
• Construct or not the pubdata in l1_commit_data depending on which mode the system config was loaded (it is set in eth_sender.toml).
• Passthrough the variable throughout the codebase wherever it was necessary.

TODOs

• Add endpoint for retrieving the pubdata.
• Create a PoC example (binary which calls said endpoint and stores the pubdata initially in a file, could be Celestia later e.g.).

[ilitteri]

This is not needed