test: cast negative zero to string

[kazuyukitanimura]

Which issue does this PR close?

Closes #1036
Related #3811

Rationale for this change

What changes are included in this PR?

How are these changes tested?

[andygrove]

@kazuyukitanimura Could you confirm the tests actually catch the negative zero case? The Rust format! macro still formats -0.0 as "-0.0" and I don't see a code change that normalizes it. It would be helpful to see the test output or add a more targeted assertion, for example a SQL file test like:

SELECT CAST(CAST('-0.0' AS FLOAT) AS STRING)

This would make it clear that Comet returns "0.0" rather than "-0.0". I tried this yesterday and saw an incompatibility that I wasn't able to fix easily.