`MultiFab.len()` #374

Job	Run time
🔄 Update Stub Files / Stubs	5m 8s
🐧 Ubuntu / Clang@6.0 w/o MPI	3m 58s
🐧 Ubuntu / Clang@14.0 w/ libc++ w/ MPI	4m 47s
🐧 Ubuntu / GNU@7.5	7m 3s
🐧 Ubuntu / GNU@10.5 Debug	14m 20s
🐧 Ubuntu / CUDA@11.2 GNU@9.4.0	5m 45s
🐧 Intel / ICPX	8m 43s
🐧 HIP / ROCm HIP 6.1	10m 58s
🐧 Intel / oneAPI SYCL 3D	10m 55s
🔎 CodeQL / Analyze (python)	3m 32s
🍏 macOS / AppleClang@14.0 w/o MPI	6m 8s
🪟 Windows / Clang w/o MPI Shared Debug	35m 8s
🔎 CodeQL / Analyze (cpp)	18m 55s
🪟 Windows / MSVC w/o MPI Static Release	1h 26m 36s
	3h 41m 56s

Provide feedback