Separate plutus-ledger/plutus-script-utils into own repo.

[locallycompact]

Could we separate plutus-script-utils and plutus-ledger into their own repositories so they can be released independently of cardano-node-emulator?

[smelc]

I personally am not in favor of having many small repos, yielding to a spread of version dependencies, versions of GHC etc.

However I do understand that it imposes a bigger toll on the update of plutus-script-utils and plutus-ledger. So I'm happy to help finish a PR that would do that, by helping on the cardano-node-emulator side.