WIP: Multiprecision Build

[oseikuffuor1]

This PR will introduce multiprecision capabilities into master.

hypre currently supports single, double and longdouble precision in independent builds. This PR will enable an interoperable build of hypre in the different precisions. This will enable mixed-precision code development in hypre. Key components include:

1. An updated build system that allows building hypre with multiprecision capabilties turned on
2. Scripts to check and update the multiprecision build
3. New header files that identify multiprecision functions
4. Mixed-precision Krylov solver capabilities
5. Capability to use a different operator for the preconditioner than the matrix operator (for Krylov solvers)

To Do:

1. Cleanup warnings/ errors on macOS, etc.
2. Fixes for memory alignment bug
3. Updated mixed-precision AMG utilizing fixes in 1.
4. Review from the hypre team