Change page define usages over to self-defined

In the case of an AArch64 builder is using 16kb or 64kb pages like is
common on servers then it would fail to compile, even if the resulting
application would only ever run on 4k page hosts.

Resolve this by removing the build check and hardcoding 4kb pages for
each of our uses. We still require 4kb pages to run, so this mostly just
removes the weirdness where it is 16kb builder + 4k runner. Would have
broken some of our assumptions when running.

FEXHeaderUtils/FEXHeaderUtils/TypeDefines.h

@@ -0,0 +1,11 @@
+#pragma once
+#include <cstddef>
+
+namespace FHU {
+  // FEX assumes an operating page size of 4096
+  // To work around build systems that build on a 16k/64k page size, define our page size here
+  // Don't use the system provided PAGE_SIZE define because of this.
+  constexpr size_t FEX_PAGE_SIZE = 4096;
+  constexpr size_t FEX_PAGE_SHIFT = 12;
+  constexpr size_t FEX_PAGE_MASK = ~(FEX_PAGE_SIZE - 1);
+}