[web] Push changeThreadSettingsAction down to ThreadSettingsPrivacyTab
Summary:
Push down changeThreadSettingsAction (and accompanying state/functionality) to ThreadSettingsPrivacyTab.
Also push down the "Save" button.
In previous diff (D3842) did the same for ThreadSettingsGeneralTab... yes there's some repeated code but I think it's the best place to put it
Depends on D3842
Test Plan:
- Open ThreadSettingsModal
- Make some changes on the Privacy tab
- Make sure that things continue to look/work as expected
Reviewers: def-au1t, palys-swm
Reviewed By: palys-swm
Subscribers: ashoat, Adrian, karol-bisztyga, yayabosh
Differential Revision: https://phabricator.ashoat.com/D3844