Enforce specifying sdk/private for apps.

All apps in master comply with this now, but new offenders
are being added daily. This will ensure compliance going
forward.

Test: build/soong/build_test.bash
Bug: 73535841

Exempt-From-Owner-Approval: cp from master
Change-Id: If28049750a9787bf455f72402e624dbddf842253
Merged-In: Id3fbb502d26d91b64480fec74e241ba77fa0faff