✨ Add pre-start hook support to manager

[leontappe]

I have a use case similar to the one described in a previous PR and this issue.

My controller needs to consume job status files on start, that would normally be worked on by a custom runnable during runtime. With vanilla controller-runtime this is currently not possible as any code that is run before reconciliation, has no access to a running manager.

This PR provides a way to register runnables as hooks that you can supply to your manager.

This PR is based on a fork of https://github.com/terinjokes/controller-runtime/tree/prestart-hook which is in turn a fork of this repo. I rebased the current master onto the latest development state of the original PR and implemented some of the proposals made by @JoelSpeed

[k8s-ci-robot]

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[linux-foundation-easycla]

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• ✅ login: leontappe / name: Leon Tappe (24887b2, 489ced4, 9c4c8f0)

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[k8s-ci-robot]

Hi @leontappe. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[troy0820]

/ok-to-test

[k8s-ci-robot]

@leontappe: 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	489ced4	link	false	/test pull-controller-runtime-apidiff

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository. I understand the commands that are listed here.