These should significantly speed up qpth in some cases when sparse matrices can be used. Here is a cusolver reference on these functions. This issue depends on the other core sparse functions being added (I think at least PR #1147, please add other dependencies here so I'll know when I can start) so I won't immediately start trying to add these. Also please post a reference if a good cusolver wrapper usage example gets added that we can use as a reference for wrapping these QR functions.

Following the naming conventions of the batched LU factorizations and solves of btrifact and btrisolve, I propose bqrfact and bqrsolve for the names and for now we can just implement them for sparse tensors.

\cc @nikitaved @pearu @cpuhrsch @jianyuh @mruberry @walterddr @IvanYashchuk @xwang233 @lezcano @vincentqb @vishwakftw @ssnl @zkolter