Replace PRODUCT_COPY_FILES with soong module

Include android.software.credentials.prebuilt.xml prebuilt_etc module
instead of using PRODUCT_COPY_FILES.

Bug: 345373198
Test: See if android.software.credentials.xml is installed in
      system/etc/permissions
(cherry picked from https://android-review.googlesource.com/q/commit:c5f7f80416eb9231416dfec03e8d497ceb43c4df)
Merged-In: Ia5519d1650b994f380aa4e31042139af999e49a7
Change-Id: Ia5519d1650b994f380aa4e31042139af999e49a7