rpc v2: `submitAndWatch` replace old messages if it's lagging (#4901)

Close https://github.com/paritytech/polkadot-sdk/issues/3076

The fix is really just that older messages are replaced if the client
can't keep up with the server instead.
Because I wanted the same functionality as `pipe_from_stream` for both
pending/subscription I added two wrapper types on-top of the types from
jsonrpsee to make it nicer.

I added a trait `Buffer` so I could still use pipe_from_stream but that
abstraction is a little leaky but only to avoid adding an identical
method/function with another strategy...