✨Move Source implementations to a single folder

[inteon]

Moves all the source logic to the same directory, making it easier to understand and refactor in the future.
Currently pkg/source/source.go contains the Channel, Informer and Func source, while the Kind source lives in the pkg/source/internal/kind.go file.

[k8s-ci-robot]

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[k8s-ci-robot]

@inteon: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-controller-runtime-apidiff	22f4a15	link	false	/test pull-controller-runtime-apidiff

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[inteon]

@alvaroaleman could you take a look at this PR too?
It should be purely code cleanup/ re-organisation.

[alvaroaleman]

Moves all the source logic to the same directory, making it easier to understand and refactor in the future.

What is or isn't easier to understand in terms of file layout extremely subjective while not mattering too much in practise due to IDE tooling. At the same time a change like this has a cost in review capacity and in that it breaks git blame. Given that there is no clear benefit but a clear cost I'm -1 to this.

[inteon]

Moves all the source logic to the same directory, making it easier to understand and refactor in the future.

What is or isn't easier to understand in terms of file layout extremely subjective while not mattering too much in practise due to IDE tooling. At the same time a change like this has a cost in review capacity and in that it breaks git blame. Given that there is no clear benefit but a clear cost I'm -1 to this.

Thanks for the feedback. I updated #2686 so it does no longer depend on this PR.