seer evm generate: Add ledger support

[karacurt]

Problem: Developers who want to achieve a higher security standard for their on-chain operations often use hardware wallets. We want to add a ledger functionality into a seer, enabling those users to perform operations with their cold wallets.

Solution: I propose we implement a --ledger flag that could be used together with any function call of deployment as an alternative to passing a --key file. This means that if the user specifies a ledger, it does not need to select a key file. The idea is to use this flag to do all operations to be signed and sent by a hardware wallet.

Example of what would be the --ledger flag:

./ERC20 deploy --rpc $RPC_URL--symbol $SYMBOL --decimals $DECIMALS--total-supply $SUPPLY  --ledger $LEDGER_ADDRESS