Accomplished using `run-clang-tidy` with `performance-move-const-arg,performance-unnecessary-value-param,modernize-pass-by-value`. Changed arguments to const references, removed them where inappropriate (e.g. sink parameters). Same with std::move. Manually reviewed each change to make sure that it makes sense, and do something more appropriate if possible.
This fixes a problem I was having where using frame advance with the debugger open would frequently cause panic alerts about invalid addresses due to the CPU thread changing MSR.DR while the host thread was trying to access memory. To aid in tracking down all the places where we weren't properly locking the CPU, I've created a new type (in Core.h) that you have to pass as a reference or pointer to functions that require running as the CPU thread.