Add tests for new experimental options

[caballa]

• [ ] for option --llpe
• [x] for option --devirt
• [x] for option --ipdse
• [ ] for option --precise-dce
• [ ] for option --ai-invariants

[caballa]

llpe has been removed while porting to llvm 10.

[caballa]

We will need tests for clam once it's integrated.