#### What type of PR is this?
/kind cleanup
/area core
#### What this PR does / why we need it:
This PR bumps all version to 2.20.0 to prepare for next development.
#### Does this PR introduce a user-facing change?
```release-note
None
```
#### What type of PR is this?
/kind cleanup
/area core
#### What this PR does / why we need it:
This is a regular updates after a new release.
#### Does this PR introduce a user-facing change?
```release-note
None
```
#### What type of PR is this?
/kind cleanup
/area core
#### What this PR does / why we need it:
Regenerate API docs and client to prevent unrelated changes from other PRs.
#### Does this PR introduce a user-facing change?
```release-note
None
```