Implement BaBSR Branching Heuristic as a new Branching Strategy

[liamjdavis]

This pull request introduces a new branching strategy, the BaBSR branching heuristic. The new change for this new heuristic includes additions to the configuration, option parsing, and engine components.

Key changes include:

Branching Strategy Implementation:

• Implemented the pickSplitPLConstraintBasedOnBaBsrHeuristic method in the Engine class to split on the ReLUs with the highest BaBSR score. [1] [2] [3]
• Added support for BaBSR heuristic in the ReluConstraint class, including methods to compute the BaBSR score. [1] [2] [3] [4] [5] [6] [7] [8] [9]

Option Parsing:

• Updated OptionParser to include babsr-heuristic as a valid branching strategy.
• Modified Options::getDivideStrategy() to handle the new babsr-heuristic strategy.

Testing:

• Added a new unit test file for Test_BaBsrSplitting.h for unit tests of the branching strategy.

[MatthewDaggitt]

I think the new option should be documented in the CHANGELOG.md file?

[liamjdavis]

Fixed!