Fix BOS error and crash on model creation error

[mvenditto]

Describe your changes

• Reuse context between text completion requests. Fixes the BOS error for Hermes and similar.
  • Closes #996
  • Addresses https://github.com/nomic-ai/gpt4all/issues/649#issuecomment-1572128068
• Fix a crash when the backend reports an error on llmodel_model_create2 and expose LLModel::SetImplementationSearchPath.
  • Closes #1062

Breaking Changes

• Removed PredictRequestOptions parameter from ITextPrediction methods.
  • IGpt4AllModel interface now exposes an LLModelPromptContext used for all the request.

  Before the context used to be recreated for each request.

• IGpt4AllModelFactory.LoadModel now can throw more specific exceptions:
  • ModelLoadException
  • ModelCreationException (with the underlying error code/message)

Issue ticket number and link

Checklist before requesting a review

• [x] I have performed a self-review of my code.
• [ ] If it is a core feature, I have added thorough tests.
• [ ] I have added thorough documentation for my code.
• [x] I have tagged PR with relevant project labels. I acknowledge that a PR without labels may be dismissed.
• [x] If this PR addresses a bug, I have provided both a screenshot/video of the original bug and the working solution.

Demo

Steps to Reproduce

Notes

[manyoso]

Is this ready?

[mvenditto]

Is this ready?

Tested a couple more things. ready now

[sdcondon]

Re the IGpt4AllModel interface change - are you absolutely sure you want to expose that low-level type as part of this high-level API? Feels like the design of this lib so far is that all of the stuff in Bindings is encapsulated and hidden away by the higher-level stuff. You'd be breaking that with this change. IMO PredictRequestOptions does serve a purpose - it's just that it should probably be scoped to a Gpt4All (or something higher-level, anyway - don't know if you've considered something like adding something along the lines of ITextPrediction IGpt4AllModel.CreatePredictionContext(opts)) rather than an individual prediction request?

[manyoso]

Is this out of date and to be closed?

[cebtenzzre]

mvenditto hasn't been active here in a long time - we can close this.