Initialize density to reference density for anelastic #6075

Job	Run time
Formatting	10s
Save-PR-Number	4s
GPU-SYCL	5m 5s
Docker	4m 56s
GPU-HIP	5m 8s
CPU (ubuntu-22.04, Release, NoOpenMP)	5m 7s
CPU (ubuntu-22.04, Debug, OpenMP)	5m 7s
GPU-CUDA	5m 8s
Lint-clang-tidy	5m 7s
CPU (ubuntu-22.04, Debug, NoOpenMP)	5m 8s
Lint-codeql	5m 19s
CPU (macos-latest, Release, NoOpenMP)	2m 8s
Lint-codespell	7s
	48m 34s

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