Simplify the repo graph

[encryptedcoins]

• Merge csl-types code into encoins-common
  • Backend-only code of csl-types can be moved to plutus-apps-extra
• Merge plutus-tx-extra code into encoins-common
• Get rid of plutus-tx-js . We can use the custom types on the front. For Tx construction, we use Lucid Evolution (the new version of Lucid) anyway.

On the front, we should have the following build sequence:

1. encoins-common
2. encoins-frontend

On the back, we should have the following build sequence:

1. encoins-common
2. plutus-apps-extra
3. encoins-core
4. cardano-server
5. encoins-relay