Extract common code to SaveChosenLockWorkerBase

* Extract common code of ChooseLockPassword.SaveAndFinishWorker and
ChooseLockPattern.SaveAndFinishWorker to the parent class.

* Make setters return this to make it easy to chain setter calls.

* Rename SaveChosenLockWorkerBase to SaveAndFinishWorker.

This will make the code changes in the next CL much easier.

Bug: 271968977
Bug: 277561275
Test: 1. Add screen lock (password/PIN/pattern) using Settings
      2. check screen lock works correctly
Change-Id: I98acd25f2dd81ab4608cc6943e4f238070003c17