[ENH] generate IDs during .add() if not provided

[codetheweb]

Closes https://github.com/chroma-core/chroma/issues/2286.

Does not update the JS client since it's in the midst of a refactor.

[github-actions[bot]]

Reviewer Checklist

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Testing, Bugs, Errors, Logs, Documentation

• [ ] Can you think of any use case in which the code does not behave as intended? Have they been tested?
• [ ] Can you think of any inputs or external events that could break the code? Is user input validated and safe? Have they been tested?
• [ ] If appropriate, are there adequate property based tests?
• [ ] If appropriate, are there adequate unit tests?
• [ ] Should any logging, debugging, tracing information be added or removed?
• [ ] Are error messages user-friendly?
• [ ] Have all documentation changes needed been made?
• [ ] Have all non-obvious changes been commented?

System Compatibility

• [ ] Are there any potential impacts on other parts of the system or backward compatibility?
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Quality

• [ ] Is this code of a unexpectedly high quality (Readability, Modularity, Intuitiveness)

[codetheweb]

Should we let a user give us IDs only sometimes, e.g. by allowing None in the ids list? My gut says no, but worth thinking about.

I don't think so, I can't think of a scenario where this would be helpful.

[codetheweb]

Superseded by https://github.com/chroma-core/chroma/pull/2699.