Add solveset, linsolve, and linear_eq_to_matrix from solveset to __init__.py
Add solveset, linsolve, and linear_eq_to_matrix from solveset to __init__.py

See #10006.

madan96/sympy,chaffra/sympy,Curious72/sympy,ChristinaZografou/sympy,oliverlee/sympy,aktech/sympy,drufat/sympy,mcdaniel67/sympy,mafiya69/sympy,jaimahajan1997/sympy,jerli/sympy,Curious72/sympy,sampadsaha5/sympy,oliverlee/sympy,Shaswat27/sympy,rahuldan/sympy,mafiya69/sympy,oliverlee/sympy,Davidjohnwilson/sympy,lindsayad/sympy,jaimahajan1997/sympy,kaichogami/sympy,Arafatk/sympy,madan96/sympy,Arafatk/sympy,postvakje/sympy,jerli/sympy,hargup/sympy,souravsingh/sympy,ga7g08/sympy,Titan-C/sympy,chaffra/sympy,mcdaniel67/sympy,skidzo/sympy,jerli/sympy,ChristinaZografou/sympy,kaichogami/sympy,yashsharan/sympy,kaushik94/sympy,rahuldan/sympy,madan96/sympy,yashsharan/sympy,rahuldan/sympy,Shaswat27/sympy,mcdaniel67/sympy,yashsharan/sympy,chaffra/sympy,ahhda/sympy,jaimahajan1997/sympy,drufat/sympy,Davidjohnwilson/sympy,hargup/sympy,hargup/sympy,Titan-C/sympy,ChristinaZografou/sympy,skidzo/sympy,sampadsaha5/sympy,Titan-C/sympy,aktech/sympy,postvakje/sympy,lindsayad/sympy,Arafatk/sympy,souravsingh/sympy,ahhda/sympy,Davidjohnwilson/sympy,Curious72/sympy,skidzo/sympy,lindsayad/sympy,ga7g08/sympy,drufat/sympy,Shaswat27/sympy,mafiya69/sympy,ahhda/sympy,aktech/sympy,kaushik94/sympy,souravsingh/sympy,kaushik94/sympy,sampadsaha5/sympy,ga7g08/sympy,postvakje/sympy,kaichogami/sympy