Sensor can only return numeric datatypes

[prairiesnpr]

A Home Assistant sensor can return multiple datatypes, but we are limited currently to only numeric types.

See:

zha/zha/application/platforms/sensor/__init__.py

Line 267 in 9945b69

def formatter(self, value: int | enum.IntEnum) -> int | float | str | None:

This came up when developing a V2 quirk, HA expects a sensor of class TIMESTAMP to return a datetime object, yet this will fail since we are casting to a float.