Given we already ensure nothing can set the zeroth register in
SetRegister(), we don't need to check if the index is zero and special
case it. We can just access the register normally, since it's already
going to be zero.
We can also replace the assertion with .at() to perform the equivalent
behavior inline as part of the API.
* get rid of boost::optional
* Remove optional references
* Use std::reference_wrapper for optional references
* Fix clang format
* Fix clang format part 2
* Adressed feedback
* Fix clang format and MacOS build
The Ryujinx macro interpreter and envydis were used as reference.
Macros are programs that are uploaded by the games during boot and can later be called by writing to their method id in a GPU command buffer.