feat(terraform): kubernetes image resources support (#16029)

* add tests

* add support for kubernetes image resources

* Update lib/modules/manager/terraform/extract.ts

Co-authored-by: Sebastian Poxhofer <secustor@users.noreply.github.com>

* added unknown resource

* added Kubernetes to Readme

* missed one spot in the Readme

* Update lib/modules/manager/terraform/readme.md

Co-authored-by: Sebastian Poxhofer <secustor@users.noreply.github.com>

* switch to toMatchObject() in tests

Co-authored-by: Sebastian Poxhofer <secustor@users.noreply.github.com>
Co-authored-by: Rhys Arkins <rhys@arkins.net>
Co-authored-by: Michael Kriese <michael.kriese@visualon.de>