tol variable used for 2 purpose: line search stop and inner solver stop

[josephsalmon]

https://github.com/QB3/sparse-ho/blob/527316d1b1a1ef8ec673121628194f7ae73e2cd2/sparse_ho/ho.py#L87

In this line the tol variable is referenced as a criterion to stop the inner solver, though it is also used later on line 204: https://github.com/QB3/sparse-ho/blob/527316d1b1a1ef8ec673121628194f7ae73e2cd2/sparse_ho/ho.py#L204 as a way to stop the line search. Both quantities are different, and may be introducing: tol_ls and tol_inner_opt would be useful. WDYT?