DOCS-2500: Add staged network policy resource pages to OSS

[ctauchen]

This PR introduces reference documentation for the StagedNetworkPolicy, StagedGlobalNetworkPolicy, and StagedKubernetesNetworkPolicy resources. These resources are being open sourced for the OSS 3.30 release.

For reviewers:

These pages are copied exactly from the CE docs, with one exception. Import statements have been changed for the OSS component locations.

Product Version(s):

Issue:

Link to docs preview:

• https://deploy-preview-1923--calico-docs-preview-next.netlify.app/calico/next/reference/resources/stagedglobalnetworkpolicy
• https://deploy-preview-1923--calico-docs-preview-next.netlify.app/calico/next/reference/resources/stagedkubernetesnetworkpolicy
• https://deploy-preview-1923--calico-docs-preview-next.netlify.app/calico/next/reference/resources/stagednetworkpolicy

SME review:

• An SME has approved this change.

DOCS review:

• A member of the docs team has approved this change.

Additional information:

Merge checklist:

• Deploy preview inspected wherever changes were made
• Build completed successfully
• Test have passed

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Lighthouse	1 paths audited Performance: 25 (🔴 down 1 from production) Accessibility: 90 (no change from production) Best Practices: 83 (no change from production) SEO: 92 (no change from production) PWA: - View the detailed breakdown and full score reports

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