Revert "Store a z-index id per-layer (#4128)"

This reverts commit 28a23372185c7a30c7790085a6a010c3cad6ad09, reversing
changes made to e992f84735a2ca166a7388d4eca69a6b4e6ee212.
6c2da0d25bConrad Irwin committed on 1/18/2024, 8:28:23 PMparent81baefb
7 files changedLine totals unavailable