Add support for OllamaChatCompletionClient to WELL_KNOWN_PROVIDERS

[Z1m4-blu3]

Discrepancy between the Autogen documentation for Ollama and the actual functionality of ChatCompletionClient.load_component.

Currently, attempting to follow the documented example:

from autogen_core.models import ChatCompletionClient

config = {
    "provider": "OllamaChatCompletionClient",
    "config": {"model": "llama3"},
}

client = ChatCompletionClient.load_component(config)

raises an error because "OllamaChatCompletionClient" is not registered in WELL_KNOWN_PROVIDERS.

Related issue number

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://github.com/microsoft/autogen/blob/main/CONTRIBUTING.md to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.