This commit migrates the fault-detector service to the chain-mon
package. This is useful because it moves towards standardizing all
of the offchain monitoring services into a single typescript package,
following the pattern that is already used in the repo.

This simplifies all of the linting and removes boilerplate, as the
services in chain-mon are all very similar and use the same
dependencies.

This also ports the tests from fault-detector to chain-mon, making
it the first tests in the repo. Longer term we could likely remove
the need to test using hardhat, but no need to do that for now.
This will make it easier to upgrade to a newer version of hardhat
as the version we are currently on only supports up to node v16
which is no longer LTS.

This change will save a bit of build time and a bit of time before
each commit because it will be one less package that needs to be
built or linted.