Add option in Range nodes to allow non-finite float values + export annotation

[MrEgggga]

I've recently been having problems with the way the inspector handles the float valueNAN and INF starting with this pull request -- existing NAN values are displayed as 0, and it is impossible to enter NAN into a field without editing the scene/resource's file by hand. This is for a good reason -- a lot of built-in nodes cause problems when one of their fields is set to NAN -- but it is limiting for user-created nodes and resources. While it's supposedly Bad Practice, I have often been using NAN as a sort of special value / undefined value because using null would require changing the field's type to Variant and making everything harder to edit, and this change to the behavior of Range nodes has made this incredibly inconvenient.

To my understanding, the best way to fix this would be to add a boolean field in Range nodes like allow_infinite (set to false by default) which when true allows the user to enter values like NAN and INF, and then add new versions of the export annotation to enable or disable this. I would personally prefer for allow_infinite to be opt-out for export fields rather than opt-in -- probably anything marked just as @export would have allow_infinite set to true by default and anything with a specified range would have allow_infinite set to false by default, with the option to change this. NaN values probably won't cause problems in most cases and users are unlikely to enter NaN or INF without meaning to. However, it'd make sense to me for the current behavior to be the default for both the fields of built-in nodes (especially those known to crash when infinite values are entered) and Range nodes in applications made with Godot.

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