Separate e2e fixture generation and validation

[damemi]

The make fixture commands currently generate and validate the fixtures in the same command. These should be separated into distinct commands (eg, make fixtures and make verify-fixtures)

It's necessary for us to regularly regenerate the fixtures (such as in a new release or when adding a new library). However the bats check that is currently combined with generation does a git diff to make sure no code changes have broken the e2e.

That's what it should do, but when it's combined with the step to regenerate fixtures, it means it will always fail. This means that the kind cluster is never deleted and makes it difficult to regenerate all fixtures at once.

Also, we should have a single command to generate all fixtures.

Related issue to refine e2e tests altogether: #93