Pr cross

[jjrodriguezaldavero]

New TCI version:

• Includes several optimizations given by profiling the algorithm with PyInstrument. Now its noticeably faster.
• Includes DMRG Cross
• Decouples the object to be decomposed into a BlackBox class that allows the following:

1. Load multivariate functions in MPS.
2. Load bivariate functions in MPO (to be generalized to multivariate functions)
3. Compose multivariate scalar functions with several MPS (such as, for example, MPS linear combinations)

Other changes:

• Modify the Interval class merging the RegularHalfOpenInterval and RegularClosedInterval into RegularInterval and the ChebyshevZerosInterval and ChebyshevExtremaInterval into ChebyshevInterval.

@juanjosegarciaripoll