Don't reuse the Chalk solver

This slows down analysis-stats a bit (~5% in my measurement), but improves
incremental checking a lot because we can reuse trait solve results.

crates/ra_ide_db/src/change.rs

@@ -362,7 +362,6 @@ impl RootDatabase {
             hir::db::GenericDefaultsQuery
             hir::db::ImplsInCrateQuery
             hir::db::ImplsForTraitQuery
-            hir::db::TraitSolverQuery
             hir::db::InternTypeCtorQuery
             hir::db::InternChalkImplQuery
             hir::db::InternAssocTyValueQuery