[ECM] Include enhanced-confirmation.xml in system image

This ensures that the source file...

    frameworks/base/data/etc/enhanced-confirmation.xml

...is included in the system image filesystem, at:

    /etc/sysconfig/enhanced-confirmation.xml

(This file is parsed by SystemConfigService and exposed through
SystemConfigManager. The exposed data is currently only used in one
place: EnhancedConfirmationService.)

Bug: 310654834
Test: manual
Change-Id: I6979be834eb04e018548db81bf6241ee8e797728
Ignore-AOSP-First: the referenced file is not in AOSP yet