Remove specifics required by Eigen prior to C++17

[cbentejac]

Description

This PR updates the code base by removing all the specifics that were required to handle Eigen objects prior to C++17. In particular, the following are removed:

• EIGEN_MAKE_ALIGNED_OPERATOR_NEW: https://eigen.tuxfamily.org/dox-devel/group__TopicStructHavingEigenMembers.html
• Aligned allocators for STL containers: https://eigen.tuxfamily.org/dox-devel/group__TopicStlContainers.html.

Any data structure or class that used Eigen aligned allocators is updated to stop using them.

Features list

• [x] Remove all EIGEN_MAKE_ALIGNED_OPERATOR_NEW declarations
• [x] Remove all aligned allocators in the declarations of STL containers
• [x] Update HashMap alias to an std::map with no aligned allocator and remove option to use an std::unordered_map instead