Fix issue introduced yesterday where the final fetch constant would never be marked as written

Reorganized SystemPageFlags for sharedmemory, each field now goes into its own array, the three arrays are page aligned in a single virtual allocation
Refactored sharedmemory a bit, use tzcnt if available when finding ranges (faster on pre-zen4 amd cpus)

src/xenia/gpu/texture_cache.h

@@ -108,7 +108,7 @@ class TextureCache {
     // generate a mask of all bits from before the first index, and xor it with
     // all bits before the last index this produces a mask covering only the
     // bits between first and last
-    uint32_t res = ((1U << first_index) - 1) ^ ((1U << (last_index + 1)) - 1);
+    uint32_t res = ((1U << first_index) - 1) ^ static_cast<uint32_t>((1ULL << (last_index + 1)) - 1ULL);
     // todo: check that this is right
 
     texture_bindings_in_sync_ &= ~res;