feat: consolidate most distros into "starter" (#2516)

# What does this PR do?

* Removes a bunch of distros
* Removed distros were added into the "starter" distribution
* Doc for "starter" has been added
* Partially reverts https://github.com/meta-llama/llama-stack/pull/2482
  since inference providers are disabled by default and can be turned on
  manually via env variable.
* Disables safety in starter distro

Closes: https://github.com/meta-llama/llama-stack/issues/2502.

~Needs: https://github.com/meta-llama/llama-stack/pull/2482 for Ollama
to work properly in the CI.~

TODO:

- [ ] We can only update `install.sh` when we get a new release.
- [x] Update providers documentation
- [ ] Update notebooks to reference starter instead of ollama

Signed-off-by: Sébastien Han <seb@redhat.com>

docs/zero_to_hero_guide/README.md

@@ -83,7 +83,7 @@ If you're looking for more specific topics, we have a [Zero to Hero Guide](#next
 1. **Build the Llama Stack**:
    Build the Llama Stack using the `ollama` template:
    ```bash
-   llama stack build --template ollama --image-type conda
+   llama stack build --template starter --image-type conda
    ```
    **Expected Output:**
    ```bash