core/memory; Migrate over SetCurrentPageTable() to the Memory class

Now that literally every other API function is converted over to the
Memory class, we can just move the file-local page table into the Memory
implementation class, finally getting rid of global state within the
memory code.

src/core/memory.h

@@ -58,6 +58,13 @@ public:
     Memory(Memory&&) = default;
     Memory& operator=(Memory&&) = default;
 
+    /**
+     * Changes the currently active page table to that of the given process instance.
+     *
+     * @param process The process to use the page table of.
+     */
+    void SetCurrentPageTable(Kernel::Process& process);
+
     /**
      * Maps an allocated buffer onto a region of the emulated process address space.
      *
@@ -401,10 +408,6 @@ private:
     std::unique_ptr<Impl> impl;
 };
 
-/// Changes the currently active page table to that of
-/// the given process instance.
-void SetCurrentPageTable(Kernel::Process& process);
-
 /// Determines if the given VAddr is a kernel address
 bool IsKernelVirtualAddress(VAddr vaddr);