Extract coinbase transaction types into mina-tx-type crate

[dannywillems]

Description

Extract coinbase transaction type structures into the new mina-tx-type crate.

Structures to move

From ledger/src/scan_state/transaction_logic/mod.rs:

• Coinbase (lines ~438-442)
• CoinbaseFeeTransfer (lines ~416-419)

Requirements

From #1665:

• The crate must be no_std compatible
• Each field must be documented with rustdoc comments

Current location

• ledger/src/scan_state/transaction_logic/mod.rs