[ecash-lib] [ecash-agora] Remove unneeded ecc parameters

Summary:
Now that we have a global Ecc instance, and new Ecc is basically a no-op, we can remove a lot of the ecc: Ecc params that are needed to use ecash-lib, simplifiying usage quite a bit.

The TxBuilder.sign function now receives a params object instead of a parameter list, which makes the code more readable.

This is a breaking change for both ecash-lib and ecash-agora, which we bundle in with the initWasm removal.

Depends on D17639.

Test Plan: CI

Reviewers: bytesofman, #bitcoin_abc

Reviewed By: bytesofman, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D17640