[Libvtrutils] Add Fixed-Point Class

[AlexandreSinger]

It may be useful in VTR to use fixed-point instead of floating point at times to prevent numerical overflows in the floating point domain from causing issues for some algorithms.

I recently created a basic implementation for the AP partial legalizer: #3148

We should create a general class in libvtrutils which will allow others to use this feature.

[AlexandreSinger]

@amin1377 FYI