Bump mistralai to > 1.0.0 in preparation for latest models such as Pixtral

[skylarbpayne]

Related to #521

Why?

Mistral has released a vision model, Pixtral. Supporting vision for Mistral in mirascope requires bumping up the version to the latest major version to take advantage of image capabilities.

What?

Migrates Mistral usage to v1.0.0, according to the migration guide.

The major changes are that the separate sync/async clients were merged into a single one with 4 separate functions under a chat attribute: complete, stream, complete_async, stream_async -- with some corresponding changes to the response formats.

Additionally, several enums were replaced with Literal types.

Additional Context

I have filed a bug related to support of the TypedDict versions of the message types: https://github.com/mistralai/client-python/issues/149

Testing

• All mistral tests pass
• Examples using mistral run; on spot check they look correct. But let me know if there's better validation I can do here.