@safe'ty of find and canFind

Change find's tests to validate usability of @safe.
Eliminate the trustedFindRR case by pushing it down a layer in the find stack of functions.
Mark unpredictableSeed as @trusted (@safe is a stretch due to all the casting) so that it can be used in @safe contexts.
Mark canFind's tests to validate usability of @safe (which lead to the unpredictableSeed change)
Basically (from what I understood), modern OS's only guarantee a segfault for accessing data in the very first memory page (usually, 0 to 4095). If you have a struct with a field at an offset larger than that, then even with a null pointer, you could access data outside of that first page, which would be unsafe, and not guarantee a pagefault.

I don't know where the discussion went from here, but the conclusion as I remembered it is that it was a QOI issue that should not be accounted for when dealing with safe.