Reorganise 'Certificate resource' page

[inteon]

This PR improves the structure of the 'Certificate resource' page.

One notable difference is the https://deploy-preview-1327--cert-manager-website.netlify.app/docs/usage/certificate/#reissuance-triggered-by-expiry-renewal section (that was actually talking about the different ways to trigger reissuance) is now moved and renamed to a "Reissuance triggered by user actions " https://deploy-preview-1327--cert-manager-website.netlify.app/docs/usage/certificate/#reissuance-triggered-by-user-actions section in the new structure.

Other changes: grouped all the sections about the different Certificate properties in the "Creating Certificate Resources" section.

Before:

• Certificate resource
• Creating Certificate Resources
• X.509 key usages and extended key usages
• Temporary Certificates while Issuing
• Rotation of the private key
  • Actions that will trigger a rotation of the private key
• Cleaning up Secrets when Certificates are deleted
• Renewal
• Additional Certificate Output Formats

After:

• Creating Certificate Resources
  • X.509 key usages and extended key usages
  • Additional Certificate Output Formats
• Issuance triggers
  • Reissuance triggered by expiry (renewal)
  • Reissuance triggered by user actions
• Issuance behavior: Temporary Certificates while Issuing
• Issuance behavior: Rotation of the private key
• Cleaning up Secrets when Certificates are deleted

Before	After

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[maelvls]

Hey. I looked at the right menu, it seems OK to me:

At first I was a bit confused by "Issuance triggers" vs. "Issuance behavior" but I could not think of any other way of presenting that.

I am happy with the refactoring.

/lgtm /approve

[jetstack-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: maelvls

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