message: Add `unset_root` to `ReferencedState`
  Summary: As title.
diff: @@ -279,6 +279,12 @@ class ReferencedState {
  }
  }
  + void unset_root() {
  + inner_struct.m_keep = false;
  + inner_struct.m_unset_allowshrinking = false;
  + inner_struct.m_unset_allowobfuscation = false;
  + }
  +
  const keep_reason::ReasonPtrSet& keep_reasons() const {
  if (!RedexContext::record_keep_reasons()) {
  // We really should not allow this.
  