feat: make postCheck hook required

[mds1]

Currently the default _postCheck hook just logs a warning, to encourage people to implement it when creating tasks (example here). It would be ideal to have a require(false, "_postCheck not implemented") instead to force an implementation.

However, this is not currently implemented because it breaks the sc_rehearsal_1, sc_rehearsal_2, and sc_rehearsal_4 tasks which we want to keep in CI. Therefore the scope of this issue is:

1. Give those tasks their own local solidity file, and have them implement an empty post-check.
2. Change all _postCheck hooks to have a reverting, default implementation (using require(false) because this prevents solidity from emitting "unreachable code" warnings)

[ShubhSensei]

May I work on this issue?

[mds1]

Yes, thank you! Just assigned you :)

[mds1]

This was completed by https://github.com/ethereum-optimism/superchain-ops/pull/266, thank you @ShubhSensei!