Implement InitialGasModel => And charge signatures

[CryptoPascal31]

This goal of this PR is to charge signatures both for size and for CPU.
It will be necessary for Post-Quantum signatures.

To sanitize and make it more clear, the PR creates a new concept of InitialGasModel:
an object that summarizes how a transaction will be charged, in Chainweb, before going to Pact.

The gas models are triggered by a rule within the Version.

Note: that this is Pact 5 only... I don't see the necessity to add complexity for porting it to Pact 4.

TODO: Create some proper unit tests

[CryptoPascal31]

From this branch: https://github.com/kda-community/pact-5/tree/post_quantum

Data: https://github.com/kda-community/pact-5/actions/runs/21116919182/artifacts/5170491977

If we consider the Github runner as representative: this would mean a signature cost of 48.5 / 2.5 = 20 Gas (ceil rounded)

I need to implement benchmark for WebAuthn too: since I expect a worse result for EC-DSA signature.

For information and records, for post-quantum SLH-DSA signatures: