refactor: Replace list_models_async with alist_models.

[daavoo]

For consistency with the rest of the API.

[codecov]

Codecov Report

❌ Patch coverage is 78.57143% with 9 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/any_llm/any_llm.py	66.66%	2 Missing ⚠️
src/any_llm/providers/cohere/cohere.py	33.33%	2 Missing ⚠️
src/any_llm/providers/groq/groq.py	33.33%	2 Missing ⚠️
src/any_llm/providers/ollama/ollama.py	50.00%	2 Missing ⚠️
src/any_llm/api.py	50.00%	1 Missing ⚠️

Files with missing lines	Coverage Δ
src/any_llm/providers/anthropic/anthropic.py	93.44% <100.00%> (ø)
src/any_llm/providers/anthropic/utils.py	87.78% <100.00%> (-0.10%)	⬇️
src/any_llm/providers/bedrock/bedrock.py	87.30% <100.00%> (ø)
src/any_llm/providers/cerebras/cerebras.py	85.00% <100.00%> (ø)
src/any_llm/providers/gemini/base.py	98.29% <100.00%> (ø)
src/any_llm/providers/huggingface/huggingface.py	83.33% <100.00%> (ø)
src/any_llm/providers/mistral/mistral.py	95.94% <100.00%> (ø)
src/any_llm/providers/openai/base.py	75.22% <100.00%> (ø)
src/any_llm/providers/together/together.py	56.16% <100.00%> (ø)
src/any_llm/providers/watsonx/watsonx.py	79.26% <100.00%> (ø)
... and 6 more

... and 2 files with indirect coverage changes

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[daavoo]

Integration tests: https://github.com/mozilla-ai/any-llm/actions/runs/17765293898/job/50487143485