sched: avoid using shareable singleton instance

[Huang-Wei]

What type of PR is this?

/kind cleanup
/sig scheduling

What this PR does / why we need it:

Using a shareable singleton instance may result in unexpected behavior - changes made by one caller is actually persisted, that changes may be unexpected by another caller.

In terms of framework.go#defaultFrameworkOptions, it's harmless in the regular flow. But in unit tests, one test's change to framework options is better isolated to other tests to avoid potential flakiness.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

[k8s-ci-robot]

@Huang-Wei: This issue is currently awaiting triage.

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[Huang-Wei]

/assign @alculquicondor

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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[chendave]

LGTM

[alculquicondor]

oops

/lgtm