Prefer global limit over model-specific default

[owais]

Fixes #1878

Changes

Prefer global limit over model-specific limit default when model-specific limit is not set.

[github-actions]

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[jtmal-signalfx]

I suppose the main question is who has already implemented this. It might be easy to miss by SDK implementors.

Otherwise I think that model-explicit > global-explicit > model-default > global-default sounds good. Unless more people think that in general global limits are too dangerous, and we'd rather only have the model-specific limits.

[owais]

We implemented this in the Python SDK and most people who reviewed it were surprised by the fact that it prefers model-specific default over user specified global.

[jtmalinowski]

Right, so when I was writing that rule I considered both cases, and went model-specific defaults, so there's a smaller chance of a user shooting themselves in the foot, by setting something globally and not understanding consequences. But good to hear that it was tested in practice, and now we now which way is preferred.