Merge pull request #9578 from cabalism/fix/solver-msg-import-tree-9562

cabal-install-solver/cabal-install-solver.cabal

...install-solver/src/Distribution/Solver/Modular/Message.hs

...-solver/src/Distribution/Solver/Types/ConstraintSource.hs

...solver/src/Distribution/Solver/Types/ProjectConfigPath.hs

cabal-install/src/Distribution/Client/ProjectConfig.hs

...l-install/src/Distribution/Client/ProjectConfig/Legacy.hs

cabal-install/src/Distribution/Client/ProjectConfig/Types.hs

cabal-install/src/Distribution/Client/ProjectPlanning.hs

cabal-install/src/Distribution/Client/ScriptUtils.hs

...tall/tests/UnitTests/Distribution/Client/ProjectConfig.hs

.../tests/UnitTests/Distribution/Client/TreeDiffInstances.hs

cabal-testsuite/PackageTests/ConditionalAndImport/cabal.out

...testsuite/PackageTests/ConditionalAndImport/cabal.test.hs

...estsuite/PackageTests/ConditionalAndImport/oops-0.project

...testsuite/PackageTests/ConditionalAndImport/oops-2.config

...testsuite/PackageTests/ConditionalAndImport/oops-4.config

...testsuite/PackageTests/ConditionalAndImport/oops-6.config

...testsuite/PackageTests/ConditionalAndImport/oops-8.config

...uite/PackageTests/ConditionalAndImport/oops/oops-1.config

...uite/PackageTests/ConditionalAndImport/oops/oops-3.config