Moved API doc to top level, removed ref section and faqs

[chrisnegus]

1. Issue, if available:

2. Description of changes:
This PR:

• Remove the FAQs section of the docs.
• Moves the "Provisioner CRD" section it up a level in the left nav and renames it "Provisioner API".
• Deletes the now-empty Reference section and associated _index file.

Much of the FAQs was outdated or already covered somewhere else. I've gone through it and will add some of that content back into other parts of the docs.

3. Does this change impact docs?

• Yes, PR includes docs updates
• Yes, issue opened: link to issue
• No

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

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[geoffcline]

it looks like there is one broken link due to the moved provisioner page

5:22:03 PM: ERROR 2021/11/27 23:22:03 [en] REF_NOT_FOUND: Ref "../../reference/provisioner-crd.md": "/opt/build/repo/website/content/en/pre-docs/cloud-providers/AWS/aws-spec-fields.md:7:23": page not found

can you fix this chris? The link should be

The [Provisioner CRD]({{< ref "../../provisioner-crd.md" >}}) supports defining

[chrisnegus]

it looks like there is one broken link due to the moved provisioner page

5:22:03 PM: ERROR 2021/11/27 23:22:03 [en] REF_NOT_FOUND: Ref "../../reference/provisioner-crd.md": "/opt/build/repo/website/content/en/pre-docs/cloud-providers/AWS/aws-spec-fields.md:7:23": page not found

can you fix this chris? The link should be

The [Provisioner CRD]({{< ref "../../provisioner-crd.md" >}}) supports defining

Yes. I can do that.

[chrisnegus]

/assign

[geoffcline]

perfect!