[IRSim][IROutliner] Adding InstVisitor to disallow certain operations.

This adds a custom InstVisitor to return false on instructions that
should not be allowed to be outlined.  These match the illegal
instructions in the IRInstructionMapper with exception of the addition
of the llvm.assume intrinsic.

Tests all the tests marked: illegal-*-.ll with a test for each kind of
instruction that has been marked as illegal.

Reviewers: jroelofs, paquette

Differential Revisions: https://reviews.llvm.org/D86976