⚠ Move arguments from Watch() & Start() to Source objects

[inteon]

⚠️ depends on #2686

This PR removes the argument pass-through that happens when starting a Source watch.
Now, the eventhandler is passed directly to the Source constructor function.
Additionally, the predicates are now passed to the handler.WithPredicates which returns a "filtered handler".

This UX change makes the setup of Sources more intuitive, makes it much easier to create a custom Source and makes Sources easier to reason about.

[sbueringer]

@inteon Are you still interested in this PR?

[k8s-ci-robot]

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[inteon]

@sbueringer I rebased the PR.

[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	9894401	link	false	/test pull-controller-runtime-apidiff

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[k8s-ci-robot]

PR needs rebase.

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