Decide the path to stable for experimental.chunkImportMap.

Current state

Vite 8.1 beta will ship an experimental option that exercises this. The Vite-side integration is not yet validated. This option is primarily for Vite, so stabilization waits on Vite.

Action items

• Land the Vite 8.1 beta integration that depends on this
• Collect feedback during the beta
• Re-evaluate after Vite-side validation

Part of: #9562