One thing that might be neat in the future is noticing differing results
while the tests are still running, and modifying the log messages to
indicate them. I can imagine situations where you would want to abort
the test run immediately after seeing the first regression.
Added the `derive` feature to the workspace serde dependency here.
Previously, the dependency was only used in the main package, which
ended up enabling the `derive` feature through transitive serde
dependencies. This is not the case for xtask, so we need to enable it
explicitly.
