v1alpha2 KEP-implementation final check

Prior to releasing COSI v1alpha2, COSI maintainers should review the KEP and ensure that our implemented APIs and behaviors match what is defined by the v1alpha2 KEP.

I anticipate zero divergence from Kube/client APIs and gRPC proto APIs compared to the KEP. If there is any divergence here, we **must** discuss to ensure we don't accidentally release API changes that are unintended.

I anticipate few (if any) changes to logic described by the KEP. If there is any divergence here, we **should** discuss. Since corner cases discovered during implementation and testing may necessitate behavior tweaks, these needn't necessarily block v1alpha2 release.

No implementation files or tests are named. Start by locating the v1alpha2 KEP and comparing its Kubernetes/client APIs, gRPC proto APIs, and described behaviors with the current implementation. Done means documenting any divergence and discussing API changes or behavior differences before release.

Written by the indexing model from the issue text.