Add logic to only call CPUManager Update() if state different than last Update()

[klueska]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

Currently, the CPUManager will call Update() into the container runtime to update its cset on every container from every pod every 10 seconds (or whatever the reconcilePeriod is set to, which is 10s by default). This patch updates this logic to only call Update() if the container's cset has changed since (1) it was first started, or (2) the last time Update() was called on it.

This PR also has the side effect of mitigating issues caused by the following since calls to Update() trigger all cgroups to be updated (and not just the cset cgroup):
opencontainers/runc#2366 (comment)

Which issue(s) this PR fixes:

Fixes #100906

Does this PR introduce a user-facing change?

NONE

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[klueska]

/cc @nolancon

[nolancon]

Makes sense & logic looks good.
One QQ on the unit testing - it looks like lastUpdateState is always empty, so then when comparing cset v lcset, we always perform the update and existing test cases are exercised - just wondering should there be some nuance added to the lastUpdateState? But that might be overkill - I'm happy to do a follow-up PR with some additional cases if you think it's worthwhile (I haven't contributed in a while! 😄)

[klueska]

Yeah, I didn't add any new unit tests (just made the old ones work). It'd be great if you did a follow up with some better testing around this, but I don't think it's strictly necessary for this one.

[nolancon]

/lgtm