ENH add Newton-Riemann solver

Implementation available at https://github.com/GillesBareilles/NewtonRiemannAccel-ProxGrad

@GillesBareilles can have a look after his defense in December

Start by reading the benchmark_lasso repository and the implementation linked at https://github.com/GillesBareilles/NewtonRiemannAccel-ProxGrad, then identify how existing solvers are integrated. Confirm the expected benchmark entry point and tests before proceeding. Done means the Newton-Riemann solver is available in this Lasso benchmark and its results are covered by the repository's validation process.

Written by the indexing model from the issue text.