allow sidecar to manage network interface

[hown3d]

What this PR does / why we need it:
This PR adds a flag manage-interface to the apiserver-proxy sidecar.

The g/g deploys the sidecar to add the kube-apiserver endpoint IP to the lo loopback device:
https://github.com/gardener/gardener/blob/726d9cf849807ae7e8b9f2c0362f8ee6570a1951/pkg/component/networking/apiserverproxy/apiserver_proxy.go#L307

With this flag we are able to mitigate this cilium issue, since we can choose an interface name that's picked up by cilium.

E.g. using dummy0 as interface name

kubectl -n kube-system exec cilium-nbtgj -- cilium-dbg statedb node-addresses
Defaulted container "cilium-agent" out of: cilium-agent, disable-rp-filter (init), config (init), mount-cgroup (init), apply-sysctl-overwrites (init), mount-bpf-fs (init), clean-cilium-state (init), install-cni-binaries (init)
Address                     NodePort   Primary   DeviceName
10.250.2.187                true       true      eth0
100.64.0.56                 false      true      cilium_host
fe80::b407:4cff:fe39:f6fa   false      true      cilium_host
100.83.126.209              true       true      dummy0

Release note:

allow sidecar to manage network interface via `manage-interface` flag

[gardener-robot]

@hown3d Thank you for your contribution.

[gardener-robot-ci-3]

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[ScheererJ]

Thanks for providing a way forward with regards to the cilium issue.

It is interesting how history seems to repeat itself as the apiserver-proxy at some time in the past used to create devices...

[axel7born]

/lgtm
I tested the change together with gardener/gardener-extension-networking-cilium#350
@ScheererJ I think, all your comments have been addressed. Do you want to have another look?

[ScheererJ]

/lgtm