refactor: Allow export prefix SchedulingContextState for use across plugins

[kfirtoledo]

The schedulingContextState type was renamed to SchedulingContextState to make it accessible from other packages and enable sharing of prefix state across different plugins.

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[k8s-ci-robot]

Hi @kfirtoledo. Thanks for your PR.

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[kfirtoledo]

/assign @liu-cong

[nirrozenbaum]

/ok-to-test

[nirrozenbaum]

this LGTM. overall the idea behind CycleState is to share state between different plugins.
for this to happen, the state struct should be public and not private (so other plugins can read it).
/approve

leaving final stamp for @liu-cong.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: kfirtoledo, nirrozenbaum

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[liu-cong]

To share this state, I think we need to make the getPrefixState also public.

[kfirtoledo]

This code will also work.

raw, err := cycleState.Read(prefix.PrefixCachePluginType)
	if err != nil {....}
prefixState, ok := raw.(*prefix.SchedulingContextState)

@nirrozenbaum also suggested a good idea to add a function like cycleState.ReadAsType to make it more generic instead of using specific get<XXX>State methods for each plugin. But in both cases, you still need to export SchedulingContextState.

[liu-cong]

This is essentially duplicating this helper function. Let's make this also public so people don't need to do the error handling and type assertion.

Otherwise this looks good to me.

[nirrozenbaum]

it won’t help to make this function public as long as it’s part of the prefix scorer.
different plugins don’t have access to the scorer, only to cycle state.

[liu-cong]

Ah, actually this method doesn't need to be a method on the prefix Plugin. It can be its own standalone helper method.

[nirrozenbaum]

if you decide to do that (not a big deal from my side if not, its 3 LoC), maybe you can extract state struct and the helper function to a different file. just to have all state related code organized together.

[kfirtoledo]

@nirrozenbaum and @liu-cong, I replaced getPrefixState with a more generic function - PTAL

[nirrozenbaum]

this looks great

[liu-cong]

/lgtm