Revert "DO NOT MERGE - [ActivityManager] Ensure consistency behavior when a background activity brings another existed activity to front."

This reverts commit a4403d3760ddec2f5f066288d02bde1ea9019132.
Revert "fix wrong transparent computation when background is transparent"

This reverts commit d8373bebd6a1da3aa2e6f4c9f447887449784671.