docs: migrate URL

[erinecon]

What this PR does

This PR migrates the RTD documentation under the Canonical domain.
This PR also contains missing project files for setting up the cookie banner for GA4 tracking.

Why we need it

URL migrations are a high priority this cycle that we need to complete ASAP.

Checklist

• I followed the contributing guide
• I added or updated the documentation (if applicable)
• I updated docs/changelog.md with user-relevant changes
• [N/A] I added a change artifact for user-relevant changes in docs/release-notes/artifacts. If no change artifact is necessary, I tagged the PR with the label no-release-note.
• I used AI to assist with preparing this PR
• [N/A] I added or updated tests as needed (unit and integration)
• [N/A] If integration test modules are used: I updated the workflow configuration
  (e.g., in .github/workflows/integration_tests.yaml, ensure the modules list is correct)
• [N/A] If this PR involves Terraform: terraform fmt passes and tflint reports no errors
• [N/A] If this PR involves Rockcraft: I updated the version