Suggested Edits: Use Drawer component on mobile
On mobile, use the Drawer component from MobileFrontend instead of OOUI's popup.
The component has a down arrow rather than an X, but this is OK per comments in
phab.
Bug: T238164
Change-Id: I2e3c740bf34bc03816560e38f531b8fdda324508
Depends-On: I4c2bd895583427dc3b4dd872d8daf9b19c5b388c