function getAllKeys(obj) {
  const keys = []
  for (; obj != null; obj = Object.getPrototypeOf(obj)) {
    keys.push(...Object.getOwnPropertyNames(obj))
  }
  return keys
}
Finds all non-symbol keys for an object and its prototype chain. Symbol keys
are not included to simplify the implementation of debugProxy.

@param {object | null} obj