Description

Extend backend support to surface timing data related to prebuilds.

This includes:

• Updating the existing workspace-level timings API to report the correct build time for prebuilds
• Adding Prometheus metrics to expose aggregated prebuild timing data across templates, organizations, and globally.

Relevant metrics to consider:

• Whether the workspace was created using a preset, a prebuild pool, or neither (regular workspaces)
• Time taken to build into the pool (initial provisioning build)
• Time taken to claim from the pool (claim provisioning build)

These reports will help users evaluate prebuild performance and better understand time savings.