fix(python): json_utils: handle sets, and unsafe integers
fix(python): json_utils: handle sets, and unsafe integers

Encode sets as lists.

Encode integers that cannot be exactly represented as 64-bit floating point numbers as strings.

janelia-flyem/neuroglancer,janelia-flyem/neuroglancer,seung-lab/neuroglancer,google/neuroglancer,google/neuroglancer,google/neuroglancer,seung-lab/neuroglancer,seung-lab/neuroglancer,google/neuroglancer,google/neuroglancer,janelia-flyem/neuroglancer,seung-lab/neuroglancer,google/neuroglancer,google/neuroglancer,seung-lab/neuroglancer,janelia-flyem/neuroglancer,seung-lab/neuroglancer,janelia-flyem/neuroglancer,seung-lab/neuroglancer,google/neuroglancer