Perform I/O on a background thread

Otherwise strictmode crashes the app.

Started logging and showing toast instead of crashing the app in few
places.

Updated UI for syncing keys so that input fields are more obvious.

MUST_SLEEP: Wasn't added in this CL.

Bug: 264864412
Test: manual
Change-Id: Ib54e9f0dd58371a6a0de8ac6bf1616f5aaac6b37