Improvements to NanoVDB #4078

Job	Run time
linux-ax:2025-clang19.1-cxx:g++-Release	4m 51s
linux-ax:2025-clang19.1-cxx:clang++-Debug	21m 12s
linux-ax:2023-clang15-cxx:g++-Release	4m 22s
macos-cxx:clang++-llvm:21-Release	14m 28s
linux-ax:2025-clang19.1-cxx:clang++-Release	4m 30s
linux-ax:2024-clang17.2-cxx:clang++-Release	4m 22s
macos-cxx:clang++-llvm:19-Release	13m 43s
macos-cxx:clang++-llvm:21-Release	16m 30s
linux-ax:2025-clang18.1-cxx:clang++-Release	4m 42s
linux-ax:2023-clang15-cxx:clang++-Release	4m 33s
macos-cxx:clang++-llvm:20-Release	14m 48s
linux-ax:2024-clang16.2-cxx:clang++-Release	4m 33s
macos-cxx:clang++-llvm:18-Release	15m 51s
macos-cxx:clang++-llvm:17-Release	16m 45s
macos-cxx:clang++-llvm:16-Release	16m 35s
gen-grammar	0s
	2h 41m 45s

Provide feedback