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>

tests/integration/conftest.py

@@ -65,7 +65,7 @@ def pytest_addoption(parser):
         help=textwrap.dedent(
             """
             a 'pointer' to the stack. this can be either be:
-            (a) a template name like `fireworks`, or
+            (a) a template name like `starter`, or
             (b) a path to a run.yaml file, or
             (c) an adhoc config spec, e.g. `inference=fireworks,safety=llama-guard,agents=meta-reference`
             """