Core: Adjust emulated memory size automatically.

Dolphin now uses the simulated memory size defined in `bi2.bin` to
adjust the memory size in the emulated console automatically.

If **Enable Emulated Memory Size Override** has been enabled by the
user, the fixed memory size specified for **MEM1** and **MEM2** are
still used as they were before.

Most retail games do not define the simulated memory size (Wii or
Triforce games), or define it to a value that matches the default 24 MiB
(GameCube games), so, in the general case, there is no behavior change.
One game that sets the simulated memory to a non-default value is the
debug build of _Mario Kart: Double Dash!!_, where the value is set to
48 MiB.

This enhancement is focused mainly to the modding community. Prior to
these changes, modded games with extended memory requirements would
fail to launch in Dolphin [with no indication of what the problem is] if
the user failed to set the emulated memory override to the correct
value. Now, modding tools can specify the simulated memory size in the
`bi2.bin` file to produce extended games that _just work_ in Dolphin,
without cumbersome instructions that can be overlooked by the user.

Source/UnitTests/Core/PowerPC/PageTableHostMappingTest.cpp

@@ -10,6 +10,7 @@
 #include "Common/Align.h"
 #include "Common/CommonTypes.h"
 #include "Common/Swap.h"
+#include "Core/ConfigManager.h"
 #include "Core/Core.h"
 #include "Core/MemTools.h"
 #include "Core/PowerPC/BreakPoints.h"
@@ -131,6 +132,8 @@ public:
     if (!EMM::IsExceptionHandlerSupported())
       GTEST_SKIP() << "Skipping PageTableHostMappingTest because exception handler is unsupported.";
 
+    SConfig::Init();
+
     auto& system = Core::System::GetInstance();
     auto& memory = system.GetMemory();
     const u32 host_page_size = memory.GetHostPageSize();
@@ -177,6 +180,8 @@ public:
     EMM::UninstallExceptionHandler();
     Core::UndeclareAsCPUThread();
     system.GetMemory().Shutdown();
+
+    SConfig::Shutdown();
   }
 
   static void SetSR(size_t index, u32 vsid)