It has been argued that the API files provide value for verifying that
code changes produce API changes in the expected way. This helps devs
and reviewers.
It has also been argued that the CI job adds friction and forces devs
to configure their environment unnecessarily.
Both viewpoints have some merit.
Lets remove the API files for now, and when we start doing 1.0-alpha
releases and can start to expect minimal API breaking changes (and
therefore minimal need to use the tooling).
We have a mechanism to run additional custom tests by way of the
`extra_tests.sh` script in each crate.
Remove the CI job and run the schemars test using `extra_tests.sh`. This
patch changes the test coverage because currently the schemars test is
only run with a stable toolchain but with this patch applied it runs
with stable, MSRV, and nightly.
Fix: #2787