frontend: Apply process mitigation policies for Windows

DEP: Enable DEP as it's still opt-in even on Windows 10. No OBS code or
plugins should be executing data as code and this is an important
mitigation against stack-based buffer overflows.

ASLR: Enable and force ASLR. This makes it harder for any potential
exploits to use fixed offsets into OBS or Windows DLLs to run gadgets.

Extension Points: Disable extension points. These are typically used for
system-wide code injection, and we have generally had trouble with
various things injecting into OBS and causing issues.

Handle Check: Enable strict handle checks when running debug builds.
This will raise an exception if we operate on an invalid handle,
something that should hopefully not ever happen in the current code.