refactor(pxe): introduce typed oracle registry for serialization

[nchamo]

Why we are doing this

The 53 oracle methods in oracle.ts each manually deserialize ACVM inputs and serialize outputs using ad-hoc patterns (Fr.fromString, toACVMField, destructuring, etc.). This transport layer also contained business logic interleaved with serialization, making the code hard to follow, error-prone, and impossible to auto-generate.

Ideally, this entire layer would be auto-generated from the Noir oracle declarations. This PR is a stepping stone toward that goal.

Our fix

Introduces a typed oracle registry (oracle_registry.ts) that describes every oracle's parameter and return types via reusable TypeMapping objects. Each TypeMapping provides bidirectional field serialization/deserialization, and the registry entry wires them together via a callHandler helper that deserializes inputs, calls the handler, and serializes the result.

Every oracle method in oracle.ts is converted to a consistent pattern:

aztec_utl_getBlockHeader(...inputs: ACVMField[][]): Promise<(ACVMField | ACVMField[])[]> {
  return callHandler({
    oracle: 'aztec_utl_getBlockHeader',
    inputs,
    handler: ([blockNumber]) => this.handlerAsUtility().getBlockHeader(blockNumber),
  });
}

With this shape, oracle.ts is ready to be fully replaced by a mechanical loop in a follow-up PR.

Additional changes:

• Adds Noir struct mirrors (BoundedVec, FixedArray, Option) so oracle return types can carry wire-format metadata needed by the ACVM serializer
• Normalizes null → undefined in getTxEffect and getCapsule handler interfaces to align with TypeScript conventions

This PR covers only the PXE oracle layer. The TXE (rpc_translator.ts) will be converted in a follow-up PR. Some serialization/deserialization logic had to move from the transport layer into the handlers, because Noir expects specific empty-value representations (e.g., zero-padded BoundedVec, discriminated Option). The new struct mirrors encapsulate this complexity so handlers don't need to think about wire formats directly.

What's next

• Getting rid of oracle.ts entirely — replacing 53 identical methods with a mechanical loop over the registry
• Real serialization tests that validate the Noir -> Typescript -> Noir roundtrip. No more "this serialization should match the one on typescript" tests
• Automatic interface generation from the registry entries
• Detecting Noir oracles that don't have a matching registry entry (compile-time safety net)

[nchamo]

The hash changed, but we didn't update the version since we actually didn't make any changes to the oracle

[nchamo]

Had to make this type of changes on this file, but in a following PR I'll apply changes similar to oracle.ts. So we can also get rid of this file

[nchamo]

DIE IMPORTS, DIE! 🔥