Rename and create admin-tools page and routing from scans

[ameliav]

🗣 Description

Rename and create admin-tools page and routing from scans.

💭 Motivation and context

The current state of the project includes the “Web Page Scan” feature, which is considered out of scope for our project goals. Additionally, we need to ensure that all dependencies, especially related to routing, are properly addressed.

🧪 Testing

• Change Scans page to Admin Tools (Only “Global Admin” Accessible)
• Update header by moving link to right-left dropdown menu
• No longer any routes directly to /scans
• /scans -> /admin-tools

📷 Screenshots

Scans is now under "Admin Tools"

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• All future TODOs are captured in issues, which are referenced
  in code comments.
• All relevant type-of-change labels have been added.
• I have read the CONTRIBUTING document.
• These code changes follow cisagov code standards.
• All relevant repo and/or project documentation has been updated
  to reflect the changes in this PR.
• Tests have been added and/or modified to cover the changes in this PR.
• All new and existing tests pass.

✅ Pre-merge checklist

• Revert dependencies to default branches.
• Finalize version.

✅ Post-merge checklist

• Create a release.

[nickviola]

LGTM

[cduhn17]

See comments. There are multiple locations where there is commented out code.

[schmelz21]

This now looks good.