Adding launch source info in the wallpaper picker intent (1/3)

When launching Wallpaper & Style from the settings search, we should
also append the launch source information to the intent.

The major purpose if for logging. So that we know then entrypoint of the
Wallpaper & Style app.

Test: Manually tested that the intent contains the extra we need
Bug: 368052505
Flag: EXEMPT bugfix
Change-Id: I9af663dad7cb79bfe74431e6a61cd34393e60dbd