✨Service interface load balancer

[mgrote]

What this PR does / why we need it:

For better testability it is useful to abstract a service interface for loadbalancers. That interface could be easily mocked e.g. with gomock for propper testing.
The same was already done for pkg/cloud/services/networking in #935.

Which issue(s) this PR fixes
Fixes #1120

Special notes for your reviewer:

TODOs:

• squashed commits
• adds unit tests

/hold

_{Michael Grote [email protected], Daimler TSS GmbH, Provider Information}

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[k8s-ci-robot]

Hi @mgrote. 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.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[tobiasgiese]

/ok-to-test

[seanschneeweiss]

This is great. Helps a lot with testing and makes the load balancer code more readable by moving out the metrics context calls.

[jichenjc]

mostly good , fix the pull-cluster-api-provider-openstack-test error we should be ready to go

[seanschneeweiss]

/lgtm

Thank you for updating the boilerplate.generatego.txt.

The previous test failed as the image used by Prow uses Go version 1.17.6.

After @mgrote updated to Go version 1.17, the generated files were accepted by the test.

[chrischdi]

/approve

Great job, also for handling the boilerplate header :-)

[mdbooth]

This looks great!
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: chrischdi, mdbooth, mgrote

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• OWNERS [chrischdi,mdbooth]

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[mgrote]

/hold cancel