Implement frontal method for solving linear system

[nikoscham]

This issue has been added to the FEAScript roadmap for the upcoming 0.2.0 release (https://github.com/orgs/FEAScript/discussions/17). The method is especially useful in problems with large sparse matrices. See the reference here https://www.chemeng.ntua.gr/courses/temp/fem/Hood-1976-International_Journal_for_Numerical_Methods_in_Engineering.pdf

Tasks

• Implement core algorithm for the frontal solver
• Integrate with FEAScript's existing matrix assembly system
• Benchmark performance vs existing solver(s)