fix #3853 addressing split packages as much as possible

[shawkins]

Description

first commit:
dsl.base -> dsl.internal
extended.run -> moves to client api as something that just leverages a KubernetesClient

second commit:
informers -> informers.impl (an odd man out in terms of naming convention)
utils -> utils.internal (and a couple more util classes were moved out of api)

I don't think I'll do anything with the classes in the client packages as this time as the split there is unavoidable to keep the Default clients in their original package.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• Feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change
• Chore (non-breaking change which doesn't affect codebase;
  test, version modification, documentation, etc.)

Checklist

• Code contributed by me aligns with current project license: Apache 2.0
• I Added CHANGELOG entry regarding this change
• I have implemented unit tests to cover my changes
• I have added/updated the javadocs and other documentation accordingly
• No new bugs, code smells, etc. in SonarCloud report
• I tested my code in Kubernetes
• I tested my code in OpenShift

[sonarqubecloud]

SonarCloud Quality Gate failed.   

10 Bugs
0 Vulnerabilities
0 Security Hotspots
122 Code Smells

47.9% Coverage
0.6% Duplication