fix(binary-codec): align confidential MPT wire fields

Description

This PR aligns confidential MPT field definitions and serialization with the canonical XRPL wire format. It corrects commitment and blinding-factor metadata while preserving hexadecimal UInt64 behavior for ordinary fields and using base-ten encoding only where explicitly declared by the field definitions.

Type of change

• Bug fix
• New feature
• Breaking change
• Documentation update
• Refactoring

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code where needed
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective
• New and existing unit tests pass locally with my changes

Changes

• Define BlindingFactor as a non-variable-length Hash256 field with the canonical ordinal.
• Correct the canonical ordinals for AmountCommitment and BalanceCommitment.
• Mark MPT amount-related UInt64 fields as base-ten in the field definitions.
• Apply base-ten UInt64 conversion only when the field metadata requires it.
• Preserve strict hexadecimal serialization for ordinary UInt64 fields.
• Add golden wire fixtures and round-trip coverage for live RPC numeric representations.

Tests

• CGO_ENABLED=1 CC=gcc go test ./binary-codec/... ./pkg/typecheck

CI status

Notes

• This PR targets the temporary confidential-transfers integration branch.
• Changelog updates are intentionally deferred until the integration branch stabilizes.