Prompt API: return the model availability status to the renderer

Previously we only returned a boolean indicating if the text session
can be created. If not, the browser process will be responsible for
posting a warning message to the console.

In this CL, the browser process will instead passing the status back
including the kAfterDownload one to match the explainer. The renderer
will add the warning message to the console when it receives the
error.

NO_IFTTT=Linting rule is recently added

Bug: 345368402
Change-Id: I03807fb4a383a58e39e0f3aac137cc5225642abd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5598605
Reviewed-by: Takashi Toyoshima <toyoshim@chromium.org>
Commit-Queue: Mingyu Lei <leimy@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1314451}