Add values to ModelStreamingResponseStatus as this is logged in UMA.

Also add comments to make this clear.

This moves kErrorSessionDestroyed which was added recently. Adding it
moved everything else. This restores things to how they were
originally.

Bug: 343094158
Change-Id: If1bf11faecf3cb2d7c5f4b484ad21b06140836be
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5579436
Reviewed-by: Mingyu Lei <leimy@chromium.org>
Commit-Queue: Fergal Daly <fergal@chromium.org>
Auto-Submit: Fergal Daly <fergal@chromium.org>
Reviewed-by: Takashi Toyoshima <toyoshim@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1307867}