feat: lit protocol key exchange

[harbu]

Summary

Add support for retrieving and storing encryption keys via lit-protocol. When enabled we will first try to retrieve / store key using lit protocol, if this doesn't work, we use our own key-exchange system.

Changes

• All lit-protocol library interactions are encapsulated into class LitProtocolFacade.
• Add new class GroupKeyManager that is used to retrieve and store encryption keys. It contains the logic for iterating over different key exchange strategies until a key is found (or successfully generated and stored).
  • Retrieve key: (1) local, (2) lit-protcol, and (3) Streamr key-exchange
  • Store key: (1) generate with lit-protocol, and if that fails, (2) generate locally. We always store encryption key into local store.

Limitations and future improvements

• lit-protocol is hard coded to work with main net Polygon and pre-defined streamRegistryChainAddress
• no integration tests for lit-protocol
  • implement in future when it becomes possible to run own nodes and override streamRegistryChainAddress and RPC settings
• Since we can't write integration tests for lit-protocol, do we need some automated tests to run against production?
• Combine encryption and decryption client config blocks

Checklist before requesting a review

• Is this a breaking change? If it is, be clear in summary.
• Read through code myself one more time.
• Make sure any and all TODO comments left behind are meant to be left in.
• Has reasonable passing test coverage?
• Updated changelog if applicable.
• Updated documentation if applicable.