Merge branch 'add-package_root-to-find_package' into release-3.9

Source/cmFindPackageCommand.cxx

Source/cmFindPackageCommand.h

Tests/RunCMake/find_package/PackageRoot-stderr.txt

Tests/RunCMake/find_package/PackageRoot.cmake

Tests/RunCMake/find_package/PackageRoot/BarConfig.cmake

Tests/RunCMake/find_package/PackageRoot/FindBar.cmake

Tests/RunCMake/find_package/PackageRoot/FindFoo.cmake

..._package/PackageRoot/foo/cmake_root/cmake/BarConfig.cmake

...nd_package/PackageRoot/foo/env_root/cmake/BarConfig.cmake

.../RunCMake/find_package/PackageRootNestedConfig-stderr.txt

Tests/RunCMake/find_package/PackageRootNestedConfig.cmake

.../RunCMake/find_package/PackageRootNestedModule-stderr.txt

Tests/RunCMake/find_package/PackageRootNestedModule.cmake

Tests/RunCMake/find_package/RunCMakeTest.cmake