This change reorganizes the `tx/transactors` directory for consistency and discoverability. There are no behavioral changes, this is a pure refactor. Underscores were chosen as the way to separate multi-words as this is the more popular option in C++ projects.
Specific changes:
- Rename all subdirectories to lowercase/snake_case (`AMM` → `amm`, `Check` → `check`, `NFT` → `nft`, `PermissionedDomain` → `permissioned_domain`, etc.)
- Merge `AMM/` and `Offer/` into `dex/`, including `PermissionedDEXHelpers`
- Rename `MPT/` → `token/`, absorbing `SetTrust` and `Clawback`
- Move top-level transactors into named groups: `account/`, `bridge/`, `credentials/`, `did/`, `escrow/`, `oracle/`, `payment/`, `payment_channel/`, `system/`
- Update all include paths across the codebase and `transactions.macro`
The invariant check system had grown into a single monolithic file pair containing 24 invariant checker classes. The large `InvariantCheck.cpp` file was a frequent source of merge conflicts and difficult to navigate. This refactoring improves maintainability and readability with zero behavioral changes.
In particular, this change:
- Splits `InvariantCheck.h` and `InvariantCheck.cpp` into 10 focused header/source pairs organized by domain under a new `invariants/` subdirectory.
- Extracts the shared `Privilege` enum and `hasPrivilege()` function into a dedicated `InvariantCheckPrivilege.h` header, so domain-specific files can reference them independently.
