feat(mistral): Enable model listing

[njbrake]

Description

Convert mistral list_models to the any-llm spec

PR Type

🆕 New Feature ## Relevant issues

Checklist

• I have added unit tests that prove my fix/feature works
• New and existing tests pass locally
• Documentation was updated where necessary
• I have read and followed the contribution guidelines```

[codecov]

Codecov Report

❌ Patch coverage is 63.63636% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/any_llm/providers/mistral/mistral.py	57.14%	3 Missing ⚠️
src/any_llm/providers/mistral/utils.py	75.00%	1 Missing ⚠️

Files with missing lines	Coverage Δ
src/any_llm/providers/mistral/utils.py	16.76% <75.00%> (-46.43%)	⬇️
src/any_llm/providers/mistral/mistral.py	43.93% <57.14%> (-46.23%)	⬇️

... and 24 files with indirect coverage changes

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