[ConstraintElimination] Rewrite tests to reduce verification complexity.

[ConstraintElimination] Rewrite tests to reduce verification complexity.

This patch reduces the bitwidth of types certain tests operate and gets
rid of a number of @use(i1) calls and xor's the conditions together
instead, which eliminates all timeouts when verifying the tests.
See https://github.com/AliveToolkit/alive2/issues/744 for more details.