This API will always succeed in creating a String representing the provided number in base-10. (cherry picked from commit dd419b5a8df3b9a32478c4a8f0ea9f70334214cd; amended to update the rest of the system. No conflicts though!)
Use IntegerStyleValue where we should; remove the ability of NumberStyleValue to hold integers, and add integer interpolation for animations.
This is in preparation of splitting off a separate IntegerStyleValue.
