llm.get_async_model(), llm.AsyncModel base class and OpenAI async models (#613)

- https://github.com/simonw/llm/issues/507#issuecomment-2458639308

* register_model is now async aware

Refs https://github.com/simonw/llm/issues/507#issuecomment-2458658134

* Refactor Chat and AsyncChat to use _Shared base class

Refs https://github.com/simonw/llm/issues/507#issuecomment-2458692338

* fixed function name

* Fix for infinite loop

* Applied Black

* Ran cog

* Applied Black

* Add Response.from_row() classmethod back again

It does not matter that this is a blocking call, since it is a classmethod

* Made mypy happy with llm/models.py

* mypy fixes for openai_models.py

I am unhappy with this, had to duplicate some code.

* First test for AsyncModel

* Still have not quite got this working

* Fix for not loading plugins during tests, refs #626

* audio/wav not audio/wave, refs #603

* Black and mypy and ruff all happy

* Refactor to avoid generics

* Removed obsolete response() method

* Support text = await async_mock_model.prompt("hello")

* Initial docs for llm.get_async_model() and await model.prompt()

Refs #507

* Initial async model plugin creation docs

* duration_ms ANY to pass test

* llm models --async option

Refs https://github.com/simonw/llm/pull/613#issuecomment-2474724406

* Removed obsolete TypeVars

* Expanded register_models() docs for async

* await model.prompt() now returns AsyncResponse

Refs https://github.com/simonw/llm/pull/613#issuecomment-2475157822

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

tests/conftest.py

@@ -75,6 +75,29 @@ class MockModel(llm.Model):
                 break
 
 
+class AsyncMockModel(llm.AsyncModel):
+    model_id = "mock"
+
+    def __init__(self):
+        self.history = []
+        self._queue = []
+
+    def enqueue(self, messages):
+        assert isinstance(messages, list)
+        self._queue.append(messages)
+
+    async def execute(self, prompt, stream, response, conversation):
+        self.history.append((prompt, stream, response, conversation))
+        while True:
+            try:
+                messages = self._queue.pop(0)
+                for message in messages:
+                    yield message
+                break
+            except IndexError:
+                break
+
+
 class EmbedDemo(llm.EmbeddingModel):
     model_id = "embed-demo"
     batch_size = 10
@@ -118,8 +141,13 @@ def mock_model():
     return MockModel()
 
 
+@pytest.fixture
+def async_mock_model():
+    return AsyncMockModel()
+
+
 @pytest.fixture(autouse=True)
-def register_embed_demo_model(embed_demo, mock_model):
+def register_embed_demo_model(embed_demo, mock_model, async_mock_model):
     class MockModelsPlugin:
         __name__ = "MockModelsPlugin"
 
@@ -131,7 +159,7 @@ def register_embed_demo_model(embed_demo, mock_model):
 
         @llm.hookimpl
         def register_models(self, register):
-            register(mock_model)
+            register(mock_model, async_model=async_mock_model)
 
     pm.register(MockModelsPlugin(), name="undo-mock-models-plugin")
     try: