Revert "Revert "Only allow root/system UIDs to send broadcast to unexported receiver""

This reverts commit 391263ce.

Reason for revert: Affected receivers have been updated to remove the RECEIVER_NOT_EXPORTED flag in ag/17597116 and ag/17575182; all other receivers using this flag are either expecting the broadcast from the local app or a protected-broadcast sent from the system UID.

Bug: 225999840
Test: atest ContextTest
Test: atest CtsSensorTestCases
Test: atest CtsAppExitTestCases
Test: atest UiTranslationManagerTest
Test: atest CtsAutoFillServiceTestCases:android.autofillservice.cts.dropdown.LoginActivityTest
Test: atest AccessibilityWindowReportingTest
Test: atest AndroidCarApiTest
Test: atest BugReportAppTest
Test: atest CarSecurityPermissionTest
Test: atest CarServiceTest
Test: atest CarServiceUnitTest
Test: atest com.android.car.obd2.test
Test: atest SampleCustomInputServiceTest
Change-Id: Ifd76ed5d84de43eeb8f5215d07e90b0952673180