Push onChangeThreadType callback down to ThreadSettingsPrivacyTab component to clean up parent ThreadSettingsModal component and to move callback closer to where it's used.
- Added threadInfo, queuedChanges, and setQueuedChanges props to ThreadSettingsPrivacyTab component so callback could be "constructed" from "within" the child component
- Adding those props also lets us determine possiblyChangedThreadType within child component instead of having to pass in from parent
Depends on D3827