XLS-96 Confidential MPT

[ckeshava]

High Level Overview of Change

This PR materializes support for Confidential MPTs in the xrpl-rust library. Here are some salient points about the design choices:

• This library makes use of the C-bindings-for-rust + shared-library of C-code generated from the mpt-crypto Github repository.
• The usage of C-bindings necessitate the "std" portion of the Rust library. ConfidentialMPTs are the first amendment which have necessitated the use of std in xrpl-rust SDK.
• This PR also adds models for transactions and requests associated with the cMPT feature.
• Although the mpt-crypto exposes 88 functions that aid in cryptography-related tasks, xrpl-rust SDK makes use of 12 of these methods for cMPT-related proof-generation transactions. Since xrpl-rust is unlikely to be used as a "validator", the verifier-methods of mpt-crypto library are exposed, by unused.

References:
Sister work in xrpl-py library: https://github.com/XRPLF/xrpl-py/pull/919/changes
mpt-crypto C library: https://github.com/XRPLF/mpt-crypto
Confidential Transfers specification: https://raw.githubusercontent.com/XRPLF/XRPL-Standards/refs/heads/master/XLS-0096-confidential-mpt/README.md

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (non-breaking change that only restructures code)
• Tests (You added tests for code that already exists, or your new feature included in this PR)
• Documentation Updates
• Release

Test Plan

New tests will be added to verify all the new additions to the xrpl-rust SDK. This includes transaction-model related integration+unit tests. It also includes tests against the Rust-wrappers around the linkage of C-shared-library.