Different mumbai aliases

[klkvr]

Right now, the most convinient way to name chains in config is by following naming used in Chains enum in ethers-rs (as discussed is foundry-rs/foundry#4895). For mumbai network this alias is mumbai (polygon-mumbai is also fine, but mumbai seems to be the preferred one)
https://github.com/gakonst/ethers-rs/blob/3e7606d81b423593db5a38dcf3b5174987efc74c/ethers-core/src/types/chain.rs#L99-L101

But following such pattern for this network results in it being non-found by StdChains, because it uses polygon_mumbai alias:

forge-std/src/StdChains.sol

Lines 204 to 206 in f18e8aa

	setChainWithDefaultRpcUrl(
	"polygon_mumbai", ChainData("Polygon Mumbai", 80001, "https://rpc-mumbai.maticvigil.com")
	);

I think that it will make sense to change alias in initializeStdChains to mumbai and fix all such differences

[mds1]

polygon_mumbai has been present for a long time, so this would be a breaking change that I'd like to avoid. Perhaps there's a way to cleanly support aliases though