refactor(tests): delete inference, safety and agents tests from providers/tests/ (#1393)

Continues the refactor of tests. 

Tests from `providers/tests` should be considered deprecated. For this
PR, I deleted most of the tests in
 - inference
 - safety
 - agents
since much more comprehensive tests exist in
`tests/integration/{inference,safety,agents}` already.

I moved `test_persistence.py` from agents, but disabled all the tests
since that test needs to be properly migrated.

## Test Plan

```
LLAMA_STACK_CONFIG=fireworks pytest -s -v agents --vision-inference-model=''
/Users/ashwin/homebrew/Caskroom/miniconda/base/envs/toolchain/lib/python3.10/site-packages/pytest_asyncio/plugin.py:208: PytestDeprecationWarning: The configuration option "asyncio_default_fixture_loop_scope" is unset.
The event loop scope for asynchronous fixtures will default to the fixture caching scope. Future versions of pytest-asyncio will default the loop scope for asynchronous fixtures to function scope. Set the default fixture loop scope explicitly in order to avoid unexpected behavior in the future. Valid fixture loop scopes are: "function", "class", "module", "package", "session"

  warnings.warn(PytestDeprecationWarning(_DEFAULT_FIXTURE_LOOP_SCOPE_UNSET))
======================================================================================================= test session starts ========================================================================================================
platform darwin -- Python 3.10.16, pytest-8.3.3, pluggy-1.5.0 -- /Users/ashwin/homebrew/Caskroom/miniconda/base/envs/toolchain/bin/python
cachedir: .pytest_cache
metadata: {'Python': '3.10.16', 'Platform': 'macOS-15.3.1-arm64-arm-64bit', 'Packages': {'pytest': '8.3.3', 'pluggy': '1.5.0'}, 'Plugins': {'asyncio': '0.24.0', 'html': '4.1.1', 'metadata': '3.1.1', 'anyio': '4.8.0', 'nbval': '0.11.0'}}
rootdir: /Users/ashwin/local/llama-stack
configfile: pyproject.toml
plugins: asyncio-0.24.0, html-4.1.1, metadata-3.1.1, anyio-4.8.0, nbval-0.11.0
asyncio: mode=strict, default_loop_scope=None
collected 15 items

agents/test_agents.py::test_agent_simple[txt=8B] PASSED
agents/test_agents.py::test_tool_config[txt=8B] PASSED
agents/test_agents.py::test_builtin_tool_web_search[txt=8B] PASSED
agents/test_agents.py::test_builtin_tool_code_execution[txt=8B] PASSED
agents/test_agents.py::test_code_interpreter_for_attachments[txt=8B] PASSED
agents/test_agents.py::test_custom_tool[txt=8B] PASSED
agents/test_agents.py::test_custom_tool_infinite_loop[txt=8B] PASSED
agents/test_agents.py::test_tool_choice[txt=8B] PASSED
agents/test_agents.py::test_rag_agent[txt=8B-builtin::rag/knowledge_search] PASSED
agents/test_agents.py::test_rag_agent[txt=8B-builtin::rag] PASSED
agents/test_agents.py::test_rag_agent_with_attachments[txt=8B] PASSED
agents/test_agents.py::test_rag_and_code_agent[txt=8B] PASSED
agents/test_agents.py::test_create_turn_response[txt=8B] PASSED
agents/test_persistence.py::test_delete_agents_and_sessions SKIPPED (This test needs to be migrated to api / client-sdk world)
agents/test_persistence.py::test_get_agent_turns_and_steps SKIPPED (This test needs to be migrated to api / client-sdk world)

```

tests/integration/inference/test_text_inference.py

@@ -9,7 +9,8 @@ import pytest
 from pydantic import BaseModel
 
 from llama_stack.models.llama.sku_list import resolve_model
-from llama_stack.providers.tests.test_cases.test_case import TestCase
+
+from ..test_cases.test_case import TestCase
 
 PROVIDER_LOGPROBS_TOP_K = {"remote::together", "remote::fireworks", "remote::vllm"}