add missing validation to notary's secret in the Attestation

[themighty1]

Currently the prover is not performing validation in the Attestation of the Notary's secret used to derive the encodings.
Relevant code:

tlsn/crates/core/src/request.rs

Line 47 in 328c2af

pub fn validate(&self, attestation: &Attestation) -> Result<(), InconsistentAttestation> {

This opens up an attack which will go like this:

• the Notary flips an encoding of a single bit and sends the encodings to the Prover
• the Prover commits (unknowingly) to the flipped encoding and gets an Attestation
• later the Prover creates a presentation and sends it to an app-specific Verifier
• the Verifier will fail or verify the encoding commitment
• the Notary will observe the failure

at best, this would be a DoS attack against the Prover
additionally, the Notary will also learn whether a certain bit was opened to the Verifier or not

[themighty1]

since we are planning to deprecate encoding commitments, it doesn't make sense to impl this, unless we reconsider deprecating it.