Improve Error Management

[gabrocheleau]

As previously discussed in #487, stringified error messages are not a reliable solution long-term.

The alernatives discussed are:

• Replacing error strings with an enum
• Extending the error object with our own custom errors
• The approach that Richard uses in Ethers v6 (custom errors with type guards)

I think that approaches 2 and 3 are better than 1 since they give us the benefit of predictable/easily testable errors (we just check the type of error) but keeping the flexibility of messages.

This is the usage that I'd have in mind:

// Usage
throw new TransactionError('Transaction reverted because gas limit was too low')

Related issue: #1440