Clarify Sidecar Buildpacks Support Status

[georgi-lozev]

Hey, CF folks,

The following commit moved the Sidecar Buildpacks documentation to archive/:

ad940a9

However, the commit does not reference any issue, story, or decision explaining why the documentation was archived.

Could you clarify:

• Are Sidecar Buildpacks / buildpack-supplied sidecars now deprecated or unsupported?
• If they are still supported, what is the current canonical documentation?
• If they are deprecated, what is the recommended replacement?

The current CAPI implementation and tests still appear to support sidecars, so the archived documentation makes the support status unclear.

[anita-flegg]

@georgi-lozev , I did a full AI check and I moved files into a new archive folder if they are not being used in the docs TOC. For files that were never added, I added them, but for files that were added but then removed, I moved them to archive. If you feel this file is still needed, please add a PR to update and move it. Then tag me and I will add it to the subnav file (TOC). Thanks.