Red code legacy MemoryManager, StreamEngine, ResourceManager, ImageHandler, AsyncPakManager, and more (#758)

Remove from CryCommon and CrySystem:
- MemoryManager and all related classes/files
- StreamEngine, ResourceManager, ImageHandler, and AsyncPakManager
- Various other related interfaces/files/classes etc. that are all now unused

Code/Framework/AzTest/AzTest/AzTest.h

@@ -17,7 +17,7 @@
 #include <array>
 
 AZ_PUSH_DISABLE_WARNING(4389 4800, "-Wunknown-warning-option"); // 'int' : forcing value to bool 'true' or 'false' (performance warning).
-#undef strdup // platform.h in CryCommon changes this define which is required by googletest
+#undef strdup // This define is required by googletest
 #include <gtest/gtest.h>
 #include <gmock/gmock.h>
 AZ_POP_DISABLE_WARNING;
@@ -477,8 +477,7 @@ int main(int argc, char** argv)
         }                                                                           \
     } while (0); // safe multi-line macro - creates a single statement
 
-// Avoid accidentally being managed by CryMemory, or problems with new/delete when
-// AZ allocators are not ready or properly un/initialized.
+// Avoid problems with new/delete when AZ allocators are not ready or properly un/initialized.
 #define AZ_TEST_CLASS_ALLOCATOR(Class_)                                 \
     void* operator new (size_t size)                                    \
     {                                                                   \