Modularise app/tx

[a1q123456]

High Level Overview of Change

This PR moves transactors and some other dependencies to libxrpl.

This PR is part of the modularisation of the transactors. See all PRs here:

• Add ServiceRegistry to help migration #6222
• Modularise WalletDB and Manifest #6223
• Modularise RelationalDB #6224
• Modularise the NetworkOPs interface #6225
• Modularise HashRouter, Conditions, and OrderBookDB #6226
• Decouple app/tx from Application and Config #6227
• Modularise app/tx #6228

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)