Migrate fully to new docs

[Jelledb]

This is still a WIP as I want to also change the file structure itself. I think by now we can use deeper nesting, e.g. /integrations/aws/landing-zones.

So taking the changes, the following todos remain for the content:

• Document this as part of another page. chore: Remove faq.projects page which is not really needed anymore after tenant move feature #1204
• Move this into a more general 'Settings' section. feat: Add new Settings category to sidebar #1194
• Move this somewhere into the docs. feat: Add new Settings category to sidebar #1194
• Move this somewhere into the docs feat: Incorporate old tenant deletion page more in the new one #1205
• Move this into a more General Settings section. feat: Add new Settings category to sidebar #1194
• Move this into a more General Settings section. feat: Add new Settings category to sidebar #1194
• Move this feat: Add IAM page as concept #1206
• Move this feat: Add new Settings category to sidebar #1194
• Decide whether this feat: Add new Settings category to sidebar #1194
• Move this feat: Add new Settings category to sidebar #1194
• Move this feat: Add new Settings category to sidebar #1194
• Make this available via sidebar => This has not been confirmed as ready yet
• Move this into Integrations > Terraform > Building Blocks feat: Document HTTP Backend as part of larger TF guide #1207
• Move this into a AWS > Building Blocks guide feat: Add BB Permission Delegation to AWS #1209
• Delete this as it is outdated chore: Remove outdated pipeline docs #1211
• Move this into Settings -> Billing Configuration feat: Add new Settings category to sidebar #1194
• Remove this as it is duplicate chore: Remove duplicate copilot page #1210
• Move this somewhere as a guide chore: More guides from Rebecca #1193

General

• Make sure we have a new welcome page (meshStack4platform engineers) feat: Introduce new welcome page #1213
• Put everything into folders as one flat structure sucks. and remove ‘new’ from everything.
• Fix all broken links. Apparently relative linking to files is the recommended method by docusaurus
• Update docs links in panel => let's only do this once this version of docs goes live. So after Wednesday. Redirects should solve it in the meantime.
• Once new structure is there, update all redirects
• Delete all old docs
• Merge this PR

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