Unbalanced LR Sinkhorn + New MBO Estimators + minor fixes

What's Changed

• Add a tuto about sparse monge displacements by @pierreablin in #374
• introduce ent_reg_cost / kl_reg_cost in Sinkhorn to clarify which is returned to the user in SinkhornOutput objects. by @marcocuturi in #376
• more precise pydocs for #376 by @marcocuturi in #377
• Update sinkhorn.py by @marcocuturi in #378
• Compute multiple soft-quantiles in one execution without using vmap by @marcocuturi in #382
• incorporate feedback in #382 by @marcocuturi in #385
• Update soft_sort.py by @marcocuturi in #387
• Add elastic-net type costs with an orthogonal linear transformation of the input before it is fed into the regularizer by @michalk8 in #383
• Add monge gap by @theouscidda6 in #361
• Feature/unbalanced LR sinkhorn by @michalk8 in #379
• changes in definition of Monge gap by @marcocuturi in #389
• fix #375, converged flag when predefined number of iterations. by @marcocuturi in #386

Full Changelog: 0.4.1...0.4.2