sandbox: add event monitor for podsandbox controller

[abel-von]

Currently the podsandbox controller has to get event monitor from CRI plugin, that makes the podsandbox controller dependent on the CRI plugin, this PR decouples it by create a event monitor for podsandbox controller independently.

[k8s-ci-robot]

Hi @abel-von. Thanks for your PR.

I'm waiting for a containerd 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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[abel-von]

needs to rebase after #9463 is merged

[abel-von]

/cc @mxpv @fuweid

[abel-von]

needs-rebase after #9617 is merged

[abel-von]

As https://github.com/containerd/containerd/pull/9617 is merged, this PR is rebased now, could you please take a look at it again? @fuweid @mxpv

[fuweid]

Will take a look in two days. Thanks!

[mxpv]

/ok-to-test

[mxpv]

@fuweid PTAL

[fuweid]

/retest