Automatic merge from submit-queue
Register the federation core API conversion and default functions.
This was removed by mistake in 9eb42f (PR #25978). Reverting some
of those changes and adding the new mechanism to autogenerate
conversions for the new types that we might define in this API
group in the future.
cc @kubernetes/sig-cluster-federation
@thockin @lavalamp please take a look at this once even if the PR merges before you get a chance to take a look.
@thockin particularly see the `federation/apis/core/v1/doc.go` file.
Fixes issue #28615
9344f2ca89