Fix remaining UB sanitizer errors

[brian-kelley]

Fix errors with ubsan. Now all tests pass in a configuration like the new ubuntu-asan-ubsan-ci build.

• replaceSumInto tests: initialize bool atomic_ member
• Fix some issues with create_reverse_map
  • Avoid shifting by negative number of bits (works in practice on tested architectures, but it's technically UB)
  • Use Kokkos::log2 to simplify an expression
  • Avoid computing log2(0)
  • Take out redundant fences
• Graph coarsening: Initialize bool member of struct. If uninitialized, its memory can contain any 8-bit value, not just 0 or 1.
• D2 coloring, VBBIT: fix color interval test. The forbidden colors considered at a time should be [color_offset, color_offset+64) with an exclusive upper bound. This matches the logic in VB.