Investigate and refactor `vm_warp_test.go` to not use an example contract

[JonathanOppenheimer]

Now that we properly test the precompiles:

Not for this PR, but is it possible to achieve the same test effect coverage by using the WarpTest.sol (and corresponding ABI/bindings) in vm_warp_test.go? If so, we could remove the ExampleWarp files all together.

I think this should be possible and pretty straightforward. The only difference is that require statements in validateWarpMessage below will need to made by the test itself, but I think that is a good change to make because otherwise the test is actually testing the example contract implementation rather than the VM behavior itself.

If you agree, could you create an issue for this? Definitely not a priority right now but don't want to lose track of it.

Originally posted by @michaelkaplan13 in ava-labs/subnet-evm#1907 (comment)

[github-actions]

This issue has become stale because it has been open 60 days with no activity. Adding the lifecycle/frozen label will cause this issue to ignore lifecycle events.

[StephenButtolph]

All of coreth and subnet-evm will be deleted after the migration to vms/saevm. Resolving this tech-debt isn't going to be worth addressing with that in mind.