- Added a workaround for misaligned SubmapSlice
	  structure between cartographer and cartographer_ros
	  built using different compilers or compile contexts
	- Rearranged SubmapSlice field order after static
	  analysis performed with clangd
	- Added commented non-portable workaround with
	  \#pragma pack
	- Closes cartographer-project#1909

Signed-off-by: Andrey Vukolov <[email protected]>

	- Adopted C++17 standard, removed CXX standard requirement
	- Removed Abseil's absl::unique_ptr in favour of std::unique_ptr
	  producing errors when built on Ubuntu 22 with fresh Abseil built
	  from source
	- Added DISABLE_AVX_ALIGNMENT CMake option to prevent Eigen
	  (especially built from source) from misalignment of the data
	  structures passed outside the library namespace on the machines
	  with modern CPUs providing AVX vectorization out of the box
	- Tested on Intel Core-i7 6700, any performance decreaseing was
	  not discovered

Signed-off-by: Andrey Vukolov <[email protected]>