Move *Picker.java and *PickerDialog.java to ui/android/java/...

There is no reason for the following files to live in content/ layer
and they should all be moved to ui/ layer.

BUG=302114

Review URL: https://codereview.chromium.org/574673003

Cr-Commit-Position: refs/heads/master@{#296637}
25 files changed