feat(cast): block --raw network selection

[mablr]

Motivation

• Follow-up feat(cast): add --network flag to cast tx for network-specific raw encoding #13745

Stacked on #13745, merge the current only after, see : #13745 (comment)

Solution

• Extracted --raw handling from Cast::block() into Cast::block_raw() for looser/specialized bound Header: Encodable.
• Removed TryIntoRlpEncodable tmp workaround
• Added specific testing for tempo to validate proper network encoding selection.

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes (it actually fixes unexpected behavior when querying non-Ethereum networks)

[zerosnacks]

👍