Reorg security docs and add more WDAC content

[sdwheeler]

PR Summary

Reorg security docs and add more WDAC content

• Fixes AB#314667

PR Checklist

• Descriptive Title: This PR's title is a synopsis of the changes it proposes.
• Summary: This PR's summary describes the scope and intent of the change.
• Contributor's Guide: I have read the contributors guide.
• Style: This PR adheres to the style guide.

[mikefrobbins]

See my comments

[learn-build-service-prod]

Learn Build status updates of commit f4af2ee:

✅ Validation status: passed

File	Status	Preview URL	Details
redir/.openpublishing.redirection.json	✅Succeeded	View (>=powershell-5.1)
reference/docs-conceptual/security/app-control/application-control.md	✅Succeeded	View (>=powershell-5.1)
reference/docs-conceptual/security/app-control/how-to-use-wdac.md	✅Succeeded	View (>=powershell-5.1)
reference/docs-conceptual/security/app-control/how-wdac-works.md	✅Succeeded	View (>=powershell-5.1)
reference/docs-conceptual/security/application-control.md	✅Succeeded	n/a (file deleted or renamed)
reference/docs-conceptual/security/overview.yml	✅Succeeded	View (>=powershell-5.1)
reference/docs-conceptual/security/security-features.md	✅Succeeded	View (>=powershell-5.1)
reference/docs-conceptual/toc.yml	✅Succeeded	View (>=powershell-5.1)

For more details, please refer to the build report.

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