Fix: move parallelize package to non-internal file

[sanposhiho]

Hello team :)

What type of PR is this?

/kind bug

What this PR does / why we need it:

move parallelize package to non-internal folder(under /framework).

---

the interface framework.Handle has Parallelizer() parallelize.Parallelizer method.
https://github.com/kubernetes/kubernetes/blob/master/pkg/scheduler/framework/interface.go#L566

Of course, custom plugins also can use framework.Handle to call framework functions.

But, in custom plugins, we cannot import parallelize.Parallelizer, because it is placed under */internal dir.

https://golang.org/doc/go1.4#internalpackages

kubernetes/pkg/scheduler/internal/parallelize/parallelism.go

Line 30 in 0ac956f

type Parallelizer struct {

It makes it hard to create mocks for framework.Handle in other repo.

alternative way

create public interface in framework package for parallelize.Parallelizer and change framework.Handle to use it.
like this:

type Handle interface {
// other methods...

	// Parallelizer returns a parallelizer holding parallelism for scheduler.
	Parallelizer() Parallelizer
}

type Parallelizer interface {
    Until(ctx context.Context, pieces int, doWorkPiece workqueue.DoWorkPieceFunc)
}

Which issue(s) this PR fixes:

Fixes #105419

Special notes for your reviewer:

Does this PR introduce a user-facing change?

NONE

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[k8s-ci-robot]

@sanposhiho: This issue is currently awaiting triage.

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[sanposhiho]

/sig scheduling

[alculquicondor]

/assign @damemi

[alculquicondor]

/approve
/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: alculquicondor, sanposhiho

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