openvdb: support searching for newer TBB headersets
The tbb_stddef.h no longer exists. In environments with older TBB
installations laying around, the superbuild's TBB ends up being found
except for the include directory because it finds the old TBB's
tbb_stddef.h header which doesn't match the superbuild's build.
Instead, also search for tbb/version.h to allow the fallback oneapi/
version extraction end up working.