[ntuple] Remove RFieldBase::GetNElements() #13046

Job	Run time
Windows 10 x64 Release	26s
Windows 10 x86 Release	1s
mac13 ARM64 LLVM_ENABLE_ASSERTIONS=On, builtin_zlib=ON	3m 45s
mac14 X64 LLVM_ENABLE_ASSERTIONS=On, CMAKE_CXX_STANDARD=20	1s
mac15 ARM64 LLVM_ENABLE_ASSERTIONS=On, CMAKE_CXX_STANDARD=20	2m 8s
mac-beta ARM64 LLVM_ENABLE_ASSERTIONS=On, CMAKE_CXX_STANDARD=20	1s
fedora40 LLVM_ENABLE_ASSERTIONS=On, CMAKE_CXX_STANDARD=20	3m 42s
Upload Event Payload	3s
alma8 LLVM_ENABLE_ASSERTIONS=On	3m 39s
alma9 LLVM_ENABLE_ASSERTIONS=On, CMAKE_BUILD_TYPE=Debug	3m 40s
ubuntu20 LLVM_ENABLE_ASSERTIONS=On	3m 39s
ubuntu22 imt=Off, LLVM_ENABLE_ASSERTIONS=On, CMAKE_BUILD_TYPE=Debug	3m 59s
ubuntu2404 LLVM_ENABLE_ASSERTIONS=On, CMAKE_BUILD_TYPE=Debug	3m 42s
debian125 LLVM_ENABLE_ASSERTIONS=On, CMAKE_CXX_STANDARD=20	3m 39s
alma9 modules_off runtime_cxxmodules=Off	3m 39s
alma9 march_native CMAKE_BUILD_TYPE=RelWithDebInfo, CMAKE_CXX_FLAGS=-march=native, CMAKE_C_FLAGS=-march=native, fortran=OFF	3m 40s
alma9 arm64 CMAKE_BUILD_TYPE=RelWithDebInfo, ccache=ON	1s
alma9-clang clang LLVM_ENABLE_ASSERTIONS=On, CMAKE_C_COMPILER=clang, CMAKE_CXX_COMPILER=clang++	3m 39s
ubuntu2404-cuda gpu	1m 17s
	44m 41s

Provide feedback