Add Cadence random in range & commit-reveal helper contract + Cadence tests

[sisyphusSmiling]

Closes: #2

ℹ️ These changes will require a redeployment of CoinToss.cdc to Testnet and an update to Xorshift128plus on Testnet & Mainnet.

Description

• Adds test coverage for Cadence coin toss implementation
• Adds RandomConsumer.cdc contract for generic commit-reveal support & random in range
  • This implementation is largely a Cadence port of the existing CadenceRandomConsumer.sol including public random in range util functions.
  • The big benefit here is that consumers no longer need to think about using a PRG as it's abstracted away into the RandomConsumer.cdc contract.
• Updates CoinToss.cdc to implement the new RandomConsumer.cdc contract and its defined constructs

[joshuahannan]

Mostly just comments about error messages. Let me know if you disagree with any of them

[sisyphusSmiling]

Thanks for all the suggestions @joshuahannan!

[tarakby]

Very useful examples, thanks for adding them 🙏🏼
I left minor comments below