Move most solver code to new module namespace

cabal-install/Distribution/Client/BuildReports/Storage.hs

cabal-install/Distribution/Client/Configure.hs

cabal-install/Distribution/Client/Dependency.hs

cabal-install/Distribution/Client/Dependency/TopDown.hs

...all/Distribution/Client/Dependency/TopDown/Constraints.hs

...l-install/Distribution/Client/Dependency/TopDown/Types.hs

cabal-install/Distribution/Client/Dependency/Types.hs

cabal-install/Distribution/Client/Fetch.hs

cabal-install/Distribution/Client/Freeze.hs

cabal-install/Distribution/Client/Get.hs

cabal-install/Distribution/Client/IndexUtils.hs

cabal-install/Distribution/Client/Init.hs

cabal-install/Distribution/Client/Init/Heuristics.hs

cabal-install/Distribution/Client/Install.hs

cabal-install/Distribution/Client/InstallPlan.hs

cabal-install/Distribution/Client/InstallSymlink.hs

cabal-install/Distribution/Client/List.hs

cabal-install/Distribution/Client/PlanIndex.hs

cabal-install/Distribution/Client/ProjectBuilding.hs

cabal-install/Distribution/Client/ProjectConfig.hs