Deduplicate SAML docs information

What does this MR do?

Moves content around between the SAML related pages to deduplicate information.

I've tried to keep the SaaS setup simpler with the more "technical" details on the self-managed page because there's more configuration required and possible for self-managed.

Also:

• removes third party images (namely Okta) to troubleshooting page
• moves vendor specific info for self-managed SAML to the SAML page.
  • Note: This makes the page longer, and it might need a bit of extra cleanup, but most of the original pages were repeated.

Related issues

Closes #298853 (closed)

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