Remove long dependency

[ejizba]

Background: We mainly use the long package because it's a dependency of our rpc packages. I'm honestly not sure how or when the long classes/types are used by customers. My hope is that they're not actually used and if we just remove them we'd be okay. Compared to undici, long is only one file and so probably has a much smaller impact on cold start.

Breaking change: Like I said, I hope long isn't used in practice. Rather than trying to verify if/when customers use it, I figure it's easier for us to just remove it in a new v5 version as a breaking change. I don't even think we need to have any replacement functionality, other than being ready to add long back if too many customers complain.

Branch to remove: ej/removeLong