Implementation of the pack theme entry in the home option

This CL aims at creating an empty entry on WPPG side. Use a local flag
to control it.

Video(Enable Flag): https://drive.google.com/file/d/1p-_aciE1D_zEQazetiBbAqPFPBNupx57/view?usp=sharing&resourcekey=0-Pl8UkCC6uM6Xl0sjWb6cBg
Video(Disable Flag): https://drive.google.com/file/d/1hV6KxVCk2aDSOOGr_26uDHMcRlVLT5Vp/view?usp=sharing&resourcekey=0-h78nI-96uQhzsdL0ZSt-wg
Bug: 398982575
Flag: EXEMPT refactor
Test: Tested by building and installing picker on local, checking if the
entry shown as expected.

Change-Id: I6e00293d04d4388d260ad01ddfbc4637bbf3cb09