Update Docs

[jshiwamV]

Update the docs in this repo

• Update the high level docs for each cloud provider explaining what gets created
• add an "unsupported" section to highlight features that are not supported in specific cloud providers - ex: we only support HMAC auth for gcp s3
• Update top level documentation to provide instructions to give an over of materialize (with links to marketing website and self-managed community edition signup, links to self-managed documentation, provide an overview of the general architecture of what gets deployed, provide a breif summary for each cloud provider.
• update contributor guide to add testing instructions

Update the Materialize documentation for Self Managed (https://materialize.com/docs)

• update version references for existing terraform - base branch off of Docs unified WIP -- do NOT merge materialize#33906 unless it has merged
• Create release note in docs https://materialize.com/docs/self-managed/v25.2/release-notes/compatibility/
• Create public release note for marketing site, highlighting the new features we support and the structural improvements