Prevent exfiltration of system files via user image settings.

This is a backport of ag/17005706.

This adds mitigations to prevent system files being exfiltrated
via the settings content provider when a content URI is provided
as a chosen user image.

The mitigations are:

1) Copy the image to a new URI rather than the existing takePictureUri
prior to cropping.

2) Only allow a system handler to respond to the CROP intent.

Bug: 187702830
Test: build and check functionality
Change-Id: Ia6314b6810afb5efa0329f3eeaee9ccfff791966
Merged-In: I15e15ad88b768a5b679de32c5429d921d850a3cb