Tests checking that TrezorSigner produces the same signatures as SoftwareSigner

[ImplOfAnImpl]

Instead of accepting impl Rng + CryptoRng directly, signing functions now accept a more specific SigAuxDataProvider, which returns auxiliary data for bip-340 nonce generation:

1. using random auxiliary data is what we did before and still do in the production code;
2. using all zeros for the data is what we do in the Trezor firmware.

So, SoftwareSigner can now be parameterized with a SigAuxDataProvider, which allows the tests to force it to produce trezor-like signatures, so that TrezorSigner's signatures can be compared against them.