Fix the Find Dialog for numeric constants and support constant with units

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Open the search function (Ctrl+F) and browse for the "NaN" constant. A dialog pops up telling you this palette item is not supported by the Find Dialog...

You can search for the "NaN" string and it will find all the NaN constants (plus all the occurrences of the "NaN" string).

You can search for all other constants (pi, machine epsilon, +/-Inf, etc.), but not for the NaN constant, which is just a numeric constant with NaN typed in it.

You can search for ALL numeric constants, but not for a specific one, say "1". Of course, you can search for all "1" strings in your code, and the constant 1 will show up among the search results, but it will be hidden in a long list of irrelevant results.

And try to search for a constant with units... You can't. What would be nice is to look for a constant irrespective of its unit, as for instance 60 s = 1 min. Did I encode that time constant as 60 s or 1 min? I need to search for 60 AND 1 to find out.