eliminate os_core, move into base; eliminate regs, move into arch abstraction layer, define x64 regs in x64 layer; move win32 backend for os core (now base) functionality to top-level win32 layer

src/base/base_system.h

@@ -0,0 +1,22 @@
+// Copyright (c) Epic Games Tools
+// Licensed under the MIT license (https://opensource.org/license/mit/)
+
+#ifndef BASE_SYSTEM_H
+#define BASE_SYSTEM_H
+
+typedef struct SystemInfo SystemInfo;
+struct SystemInfo
+{
+  U32 logical_processor_count;
+  U64 page_size;
+  U64 large_page_size;
+  U64 allocation_granularity;
+  String8 machine_name;
+};
+
+////////////////////////////////
+//~ rjf: @per_os_impl System Info
+
+internal SystemInfo *get_system_info(void);
+
+#endif // BASE_SYSTEM_H