Add isnan and iszero for FLOAD and DOUBLE

[sarutak]

Is your feature request related to a problem or challenge?

In Datafusion, +NaN and -NaN are distinguished as well as +0.0 and -0.0.
For example, asin(10) returns NaN but 'inf'::DOUBLE / 'inf'::DOUBLE returns -NaN.
3.0 * 0 returns 0.0 but -3.0 * 0 returns -0.0.

So, users need to determine NaN and 0.0 like as follows.

SELECT ... WHERE x = 'NaN'::DOUBLE OR x = -'NaN'::DOUBLE;

To avoid such boilerplate code, I propose to add isnan and iszero.

Describe the solution you'd like

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Describe alternatives you've considered

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Additional context

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