refactor(test): move tools, evals, datasetio, scoring and post training tests (#1401)

All of the tests from `llama_stack/providers/tests/` are now moved to
`tests/integration`.

I converted the `tools`, `scoring` and `datasetio` tests to use API.
However, `eval` and `post_training` proved to be a bit challenging to
leaving those. I think `post_training` should be relatively
straightforward also.

As part of this, I noticed that `wolfram_alpha` tool wasn't added to
some of our commonly used distros so I added it. I am going to remove a
lot of code duplication from distros next so while this looks like a
one-off right now, it will go away and be there uniformly for all
distros.

llama_stack/env.py

@@ -0,0 +1,24 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+import os
+
+
+class MissingCredentialError(Exception):
+    pass
+
+
+def get_env_or_fail(key: str) -> str:
+    """Get environment variable or raise helpful error"""
+    value = os.getenv(key)
+    if not value:
+        raise MissingCredentialError(
+            f"\nMissing {key} in environment. Please set it using one of these methods:"
+            f"\n1. Export in shell: export {key}=your-key"
+            f"\n2. Create .env file in project root with: {key}=your-key"
+            f"\n3. Pass directly to pytest: pytest --env {key}=your-key"
+        )
+    return value