Update K8s tutorial to start with charmcraft init

[dwilding]

Best to wait until after Charmcraft 4.0 has been released

In canonical/charmcraft#2242 we're refreshing the kubernetes profile of charmcraft init - this should become available in Charmcraft 4.0. The K8s tutorial in Ops would require less manual work if we start from the new profile instead of an empty charm.

I'm planning to do this work afer a few more profile changes:

• Switch the kubernetes and machine profiles to use the uv plugin
  feat(templates): use uv for testing and packing kubernetes and machine charms charmcraft#2312
• Switch to our new standard for tox envs
  feat: merge the 'static' tox environment into the 'lint' one charmcraft#2405
• Switch the profiles to use Jubilant for integration tests
  feat(templates): use Jubilant for integration tests of K8s and machine profiles charmcraft#2430