xpkg push

[lsviben]

Description of your changes

Moved a simplified version of crossplane push provider/configuration to crossplane xpkg push.

Not moving the whole up xpkg push, at least for now.
The new version also supports functions, while the old one should be deprecated in time.

Fixes #4669

I have:

• Read and followed Crossplane's contribution process.
• Added or updated unit and E2E tests for my change.
• Run make reviewable to ensure this PR is ready for review.
• Added backport release-x.y labels to auto-backport this PR, if necessary.
• Opened a PR updating the docs, if necessary.
  Docs PR for CLI will be done separately in Improve discoverability (add docs and pointers) for installing Crossplane CLI #4671

How has this been tested

Ran kubectl crossplane push provider <tag> and the new kubectl crossplane xpkg push <tag> and got the same result.

[phisco]

Trying to diff this w.r.t. up xpkg push as defined here:

• up supports all the upbound.Flags, which allow to specify Upbound specific settings to access the marketplace, we won't
• up creates a repository in the marketplace if it doesn't exist (--create true), we won't
• up supported passing multiple packages, we won't.
• up inferred desired annotations and applied them for flattened packages as introduced here, we won't

Diffing with crank push <configuration|provider> as defined here the only difference is that we are removing the resource specific subcommand.

[phisco]

Do we want to deprecate crank build|push?

[lsviben]

Do we want to deprecate crank build|push?

Makes sense. We can do in in a separate pr?