Improve naming for mirrored layer roots

Add the "mirrorfrom" layer's name when creating a mirror root and be
consistent with the name of the mirror surfacecontrol object created in
Java.

Bug: 424176214
Flag: EXEMPT refactor
Test: presubmit
Change-Id: Ife6544617e6a29bfbb15668cfa6bf5ecd2be6d40