[RESTRICT AUTOMERGE] Restrict ApnEditor settings

- Finish ApnEditor settings if user is not an admin

- Finish ApnEditor settings if user has DISALLOW_CONFIG_MOBILE_NETWORKS restriction

Bug: 279902472
Test: manual test
atest -c ApnEditorTest
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:e3b554b29674ef20946451d0b46d3213838e753d)
Merged-In: Iecdbbff7e21dfb11e3ba385858747a220cfd3e04
Change-Id: Iecdbbff7e21dfb11e3ba385858747a220cfd3e04