fix: Saving JSON/YAML of Layer Config

feat: separate indexes and PineconeIndex

test_from_file_invalid_config()

test_from_file_with_llm()

And some improvements where we make sure that temp files are definitely deleted after use.

Saving Layer Configs as JSON or YAML config files by representing the LayerConfig object as a dict and then turning into JSON/YAML wasn't working.

See issue here: https://github.com/aurelio-labs/semantic-router/issues/144

The issue was that, by attempting this, we were attempting to serialize all objects included in the Layer, including Routes, and the LLMs that those Routes use.

In the case of the above issue, the LLM was a Cohere one, which included a Client as one of its attributes, and this Client is not serializable.

So, instead of attempting to represent the entire LLM object a dict, to then be converted into JSON/YAML, we only keep key information about the LLM:

'module': self.llm.__module__,
'class': self.llm.__class__.__name__,
'model': self.llm.name

This is what's saved in route.py, and then sent to layer.py to be serialized (in LayerConfig.to_file()).

Then, when it comes time to load from the file via LayerConfig.from_file, the LLM is re-initialized dynamically.

Using index.describe instead of shape[].

The RouteLayer.categories() attribute has been removed, removing parts that reference this attribute form the tests.

RouteLayer.remove() renamed to delete().

Merge branch 'indices_classes' of https://github.com/aurelio-labs/semantic-router into indices_classes

Mostly just trying to make MyPy happy!

feat: Added support for MistralAI API. This includes a

Rather than is_index_populated.

installed poetry and ran make.  added mistralai to the pyproject.toml (first time using poetry, nice tool)

fix: issue #94 added from clause to the exception statement in