refactor: Better typing of ProviderMetadata and intelligent test skip

[njbrake]

• Introduced ProviderMetadata class for better structure and type safety.
• Updated provider implementations to utilize the new metadata structure.
• Simplified response conversion logic by moving it to a dedicated utility function.
• Adjusted tests to reflect changes in provider metadata access and response handling.

[codecov]

Codecov Report

❌ Patch coverage is 84.61538% with 14 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/any_llm/provider.py	62.50%	3 Missing ⚠️
src/any_llm/providers/mistral/utils.py	0.00%	2 Missing and 1 partial ⚠️
src/any_llm/utils/instructor.py	80.00%	1 Missing and 1 partial ⚠️
tests/integration/test_streaming.py	50.00%	1 Missing and 1 partial ⚠️
src/any_llm/providers/cerebras/cerebras.py	75.00%	1 Missing ⚠️
src/any_llm/providers/groq/groq.py	75.00%	1 Missing ⚠️
src/any_llm/providers/sambanova/sambanova.py	66.66%	1 Missing ⚠️
src/any_llm/providers/together/together.py	75.00%	1 Missing ⚠️

Files with missing lines	Coverage Δ
src/any_llm/providers/anthropic/anthropic.py	89.09% <100.00%> (+0.20%)	⬆️
src/any_llm/providers/aws/aws.py	86.56% <100.00%> (+0.20%)	⬆️
src/any_llm/providers/azure/azure.py	65.38% <100.00%> (ø)
src/any_llm/providers/cohere/cohere.py	64.28% <100.00%> (ø)
src/any_llm/providers/databricks/databricks.py	100.00% <100.00%> (ø)
src/any_llm/providers/deepseek/deepseek.py	65.00% <100.00%> (ø)
src/any_llm/providers/fireworks/fireworks.py	81.66% <100.00%> (ø)
src/any_llm/providers/google/google.py	85.71% <100.00%> (+0.15%)	⬆️
src/any_llm/providers/huggingface/huggingface.py	71.73% <100.00%> (ø)
src/any_llm/providers/inception/inception.py	100.00% <100.00%> (ø)
... and 25 more

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