Refactor `CardanoNetwork` entity

[jpraynaud]

Why

We want to have only one CardanoNetwork implementation in the repository when it is currently implemented in multiple crates.

What

Refactor the CardanoNetwork entity to be the unique and reusable implementation.

How

• Make the CardanoNetwork accessible from the client library
• Remove the TESTNET_MAGIC_ID constant which is not used any more
• Merge the DevNet variant into the TestNet variant
• Suppress the --cardano-mode usage in the devnet and cli runner module
• Provide bijective conversion from ProtocolMagicId to CardanoNetwork
• Can we remove the from_code function and use the conversion from ProtocolMagicId?
• Use this implementation in the snapshot converter automatic detection of the Cardano network in the client CLI.
• Convert the usage of DevNet variant in the aggregator databases if any?