Add trait for chainspec parsing

[mattsse]

we have

reth/bin/reth/src/commands/p2p/mod.rs

Lines 37 to 40 in 068bf57

	default_value = SUPPORTED_CHAINS[0],
	value_parser = chain_value_parser
	)]
	chain: Arc<ChainSpec>,

which conflicts with eth and ethereum

reth/crates/node/core/src/args/utils.rs

Lines 23 to 28 in 068bf57

	#[cfg(feature = "optimism")]
	/// Chains supported by op-reth. First value should be used as the default.
	pub const SUPPORTED_CHAINS: &[&str] = &["optimism", "optimism-sepolia", "base", "base-sepolia"];
	#[cfg(not(feature = "optimism"))]
	/// Chains supported by reth. First value should be used as the default.
	pub const SUPPORTED_CHAINS: &[&str] = &["mainnet", "sepolia", "goerli", "holesky", "dev"];

this should be abstracted via a helper trait that
a) defines the default supported traits as const
b) defines a valueparser for the chainspec type

something like:

trait ChainSpecParser: TypedValueParser< Value = ChainSpec> + Default  {
   const SUPPORTED_CHAINS : ...
} 

should be defined in crates/cli/cli crate

[loocapro]

Can I?