Fix: Update wallet_propose method to use ED25519 as the default algorithm

[ckeshava]

High Level Overview of Change

This PR aims to bring consistency between client library behavior and the rippled CLI's wallet_propose RPC. This PR needs to be viewed in conjunction with XRPLF/xrpl-py#770, XRPLF/xrpl-dev-portal#2844. The client libraries use ed25519 as the default algorithm for Wallet-related methods, unlike rippled CLI which uses secp256k1 algorithm.

Note: keyPairForSignature method still uses secp256k1 as the default cryptographic signing algorithm. I have not made any changes such internal methods.

Context of Change

Since this is a breaking-change, I expect that I need to document this change somewhere in a CHANGELOG. But I'm not sure of the exact filename.

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)
• Performance (increase or change in throughput and/or latency)
• Tests (you added tests for code that already exists, or your new feature included in this PR)
• Documentation update
• Chore (no impact to binary, e.g. .gitignore, formatting, dropping support for older tooling)
• Release

API Impact

• Public API: New feature (new methods and/or new fields)
• Public API: Breaking change (in general, breaking changes should only impact the next api_version)
• libxrpl change (any change that may affect libxrpl or dependents of libxrpl)
• Peer protocol change (must be backward compatible or bump the peer protocol version)

I don't expect any impact on the performance of the wallet_propose RPC. ed25519 algorithm is expected to be more efficient than secp256k1.

[mvadari]

This is a breaking change and shouldn't be done without an API version bump.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.9%. Comparing base (9d58f11) to head (969bcaa).

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #5186     +/-   ##
=========================================
- Coverage     77.9%   77.9%   -0.0%     
=========================================
  Files          782     782             
  Lines        66616   66615      -1     
  Branches      8161    8137     -24     
=========================================
- Hits         51902   51893      -9     
- Misses       14714   14722      +8     

Files with missing lines	Coverage Δ
src/xrpld/rpc/handlers/WalletPropose.cpp	90.9% <100.0%> (ø)

... and 5 files with indirect coverage changes