Move APIServerSource to v1

[capri-xiyue]

Problem
We need to promote APIServerSource to v1.
Some tasks this will entail, and can probably be done in different PRs.

• - v1 types with UTs
• - add new version to CRD
• - defaulting and conversion webhook
• - Update docs and examples (most in knative/docs)
• - Migrate reconciler to v1 with UTs
• - Update e2e tests to use v1
• - Create issue to make v1 the storage version and add it in migration tool in next release

Persona:
developer

Exit Criteria
APIServerSource in v1

[capri-xiyue]

/assign @capri-xiyue