Fix type-checking of select to handle non-concrete condition type
Testing SROA I discovered that the current type-checking procedure for ternary nodes fails to type-check select if the condition's type is not concrete yet.
For example, on main the new example products.hir fails to compile with
cargo run --bin hercules_driver -- hercules_samples/products.hir "SROA Xdot(true)"(though if the passes are only Xdot(true) type-checking succeeds).
