Organize ambient architecture doc

[linsun]

Some discussion from #14994 (comment) where we may likely need to have multiple pages under ambient architecture. Open this to capture thoughts and actions.

Architecture:

• Overview
• API
  • Authorization Policy
• Deep Dive

cc @craigbox @bleggett

[bleggett]

#15004 does this as a matter of course.

I think we do need at least 2 subheadings based on content we already have, as @craigbox 's doc already pointed out:

• Architecture
  • Traffic Redirection
  • HBONE

[craigbox]

• Labels: should move under a "Adding your workload to the ambient mesh" page under /docs/ambient/usage/ ?
• Layer 7 policy attachment to waypoints: should move to an "Attaching policy to waypoints" under /docs/ambient/usage/waypoints/, but I'm confused as I would expect to attach policy to workloads, not waypoints
• Traffic routing: make this a sub-page of architecture?

[bleggett]

Labels: should move under a "Adding your workload to the ambient mesh" page under /docs/ambient/usage/ ?

Yes please.

Something like

### Labels
#### Adding Workloads To Ambient Dataplane
(talk about adding `dataplane-mode` labels)
#### Enforcing L7 Policies In Ambient
(talk about adding `use-waypoint` labels) -> link to `Layer 7 Policy Attachment` subdoc

Layer 7 policy attachment to waypoints: should move to an "Attaching policy to waypoints" under /docs/ambient/usage/waypoints/, but I'm confused as I would expect to attach policy to workloads, not waypoints

I think if we breadcrumb from "for L7 policy, add a waypoint with this label" -> "then see this doc for applying L7 policy (to that waypoint)" it will be clear.

Or we can inline L7 policy and not have a "waypoint" section at all, since nobody cares about waypoints, outside of them being sine ne qua non for L7 policy.

[linsun]

Maybe complete now?

[craigbox]

https://istio.io/latest/docs/ambient/architecture/ is now only a table of contents with subpages, a good base to build from.