Per XLS-0095, we are taking steps to rename ripple(d) to xrpl(d).
C++ include guards are used to prevent the contents of a header file from being included multiple times in a single compilation unit. This change renames all `RIPPLE_` and `RIPPLED_` definitions, primarily include guards, to `XRPL_`. It also provides a script to allow developers to replicate the changes in their local branch or fork to avoid conflicts.
* Rename ASSERT to XRPL_ASSERT
* Upgrade to Anthithesis SDK 0.4.4, and use new 0.4.4 features
* automatic cast to bool, like assert
* Add instrumentation workflow to verify build with instrumentation enabled
* Copy Antithesis SDK version 0.4.0 to directory external/
* Add build option `voidstar` to enable instrumentation with Antithesis SDK
* Define instrumentation macros ASSERT and UNREACHABLE in terms of regular C assert
* Replace asserts with named ASSERT or UNREACHABLE
* Add UNREACHABLE to LogicError
* Document instrumentation macros in CONTRIBUTING.md
