perf: Prevent deferring filters with remote functions

[TrevorBergeron]

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Fixes #<issue_number_goes_here> 🦕

[tswast]

I'm a little bit concerned about hard coding remote function op here. Would it be better to flag each scalar operator as "expensive" / "cheap"?

Certainly there's a spectrum of costs possible, but a distinction could be made if there's an associated cost (e.g. cloud run CPU in this case) per call.

For example, LLM-style ops, BQML prediction (though that's not a scalar in BigQuery terms, though maybe could be in Bigframes eventually), could similarly have an "there's an extra cost associated here" flag.