llms: extract common llms errors to shared declaration

[wgeorgecook]

PR Checklist

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• [x] Name your Pull Request title clearly, concisely, and prefixed with the name of the primarily affected package you changed according to Good commit messages (such as memory: add interfaces for X, Y or util: add whizzbang helpers).
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This addresses the comment Travis made in this PR I previously made. It specifically extracts the ErrorIncompleteEmbedding error and the ErrorEmptyResponse error used in the files in the /llms directory.

I specifically targeted these errors because they're the ones I encountered using LangChain Go, there is still more work to be done in consolidating all of the other potentially shared errors.

[wgeorgecook]

Looks like the ci lint wasn't run before these files made it into main. I'm working on fixing them all now.

[wgeorgecook]

CI is now passing.