Remove Ledger-API interaction from daml-helper

[samuel-williams-da]

Daml 3 only.

The following daml-helper commands are to be fully removed, as they will be replaced with the new daml assistant.

• start
• deploy
• list parties
• list packages
• allocate party
• upload dar
• fetch dar
• reset ledger
• export ledger
• sandbox

We should also removed hs bindings if we can.

This task can only be done when we have a suitable replacement for at least daml sandbox, which is used extensively in daml tests.
Other commands may also be required.