The Write functions are used slightly less than the Read functions,
which make these a bit nicer to move over.
The only adjustments we really need to make here are to Dynarmic's
exclusive monitor instance. We need to keep a reference to the currently
active memory instance to perform exclusive read/write operations.
Avoids directly relying on the global system instance and instead makes
an arbitrary system instance an explicit dependency on construction.
This also allows removing dependencies on some global accessor functions
as well.
Gets rid of the largest set of mutable global state within the core.
This also paves a way for eliminating usages of GetInstance() on the
System class as a follow-up.
Note that no behavioral changes have been made, and this simply extracts
the functionality into a class. This also has the benefit of making
dependencies on the core timing functionality explicit within the
relevant interfaces.
Like the barrier, this is owned entirely by the System and will always
outlive the encompassing state, so shared ownership semantics aren't
necessary here.
This will always outlive the Cpu instances, since it's destroyed after
we destroy the Cpu instances on shutdown, so there's no need for shared
ownership semantics here.
