Reland "Avoid moving old-gen object to young-gen in generational CMC"

This reverts commit b53c968c4b4218cbee554de3ad1c9c630a9b6b2e.

Reason for revert: Fix non-gen CMC failures and few other trivial changes.

Change-Id: I1f9f5c5b504e654fcbb08a48114e96dfd8b25603
Test: ART_USE_READ_BARRIER=false art/tools/run-libcore-tests.sh --mode=host --variant=X64 --debug --gcstress
Test: ART_USE_READ_BARRIER=false ART_USE_GENERATIONAL_GC=false art/test/testrunner/testrunner.py --host
Test: atest CtsPackageManagerTestCases (on aosp cuttlefish device)
Bug: 392794369