EXRLoader: Support additional attribute types

[WestLangley]

Fixes #19105.

/ping @sciecode I am concerned that parseValue() does not appear to differentiate between int and Uint. But I think this PR OK for now.

[sciecode]

Yeah, parseValue should be using a Int32 not Uint32. It's not a breaking bug, but we can fix it later just to make sure it is correct.

Should be as simple as creating parseInt32 function and using in the correct places, in this case Rational and Int header values.

But PR is good, we can merge 👍

As a side note, I've created a utility function to help loaders parse data, unfortunately it's on hold until we drop examples/js support, ideally we want to remove all this type parsing from inside the loader implementation. https://github.com/sciecode/three.js/blob/dev-datautils/examples/jsm/utils/DataParser.js

[mrdoob]

Thanks!