[epic] Remove `olm.bundle.mediatype` FBC property and `plain+v0` bundle support

[everettraven]

Now that we are planning on supporting only simple registry+v1 bundles for v1.0.0 we need to ensure we remove any logic associated with supporting different bundle types from the ClusterExtension controller.

This does not mean more bundle types will not be supported in the future, but for v1.0.0 we are only going to support simple registry+v1 bundles and logic to support additional bundle types can be added in future iterations. For more information on what a "simple registry+v1 bundle" is see #734

Issues

• Remove plain+v0 support from ClusterExtension #823
• Docs: Remove olm.bundle.mediatype FBC property and plain+v0 bundle support #824

Pull Requests

• ⚠ remove olm.bundle.mediatype property and clusterextension support for plain+v0 #822