Add a test checking that ART Metrics are enabled in ART's CMC collector.

ART GC Metrics are currently only enabled in ART's Concurrent Copying
(CC) collector; add a test to ensure this is and will still be true.

(cherry picked from commit a642d2b2f1b812cdc6bc9683b59112ad54f085d8)

Test: ART_USE_READ_BARRIER=true ART_USE_GENERATIONAL_CC=true \
        m test-art-host-gtest-art_runtime_tests
Test: ART_USE_READ_BARRIER=true ART_USE_GENERATIONAL_CC=false \
        m test-art-host-gtest-art_runtime_tests
Test: ART_USE_READ_BARRIER=false \
        m test-art-host-gtest-art_runtime_tests
Bug: 270391874
Change-Id: I00bc64fdb665fe1a61b7b571963231ae51e82fea
Merged-In: I00bc64fdb665fe1a61b7b571963231ae51e82fea
2 files changed