Revise qml import path passing to tools like qmllint, qmlcachegen

Context
https://git.qt.io/alcroito/qt6-cmake-api-review/-/commit/14b4999bc857f5402a3577fe334ebfb3602ad0c2#f3ff9c1b48af14adf093e2af0c5cf2849829bb6d_149_201

If we are trying to run qmllint on a qml file belonging to $backing_target and $backing_target is an executable, CMake should pass -I ${CMAKE_CURRENT_BINARY_DIR} of the executable to qmlint.
Same should be done for qmlcachegen and other tooling.

If we are trying to run qmllint on a qml file belonging to a library, not an executable, we need to use the backtracking algorithm that Ulf suggests.
i.e. Remove TARGET_PATH from the end of CMAKE_CURRENT_BINARY_DIR
Details in context link. Search for 'OPTION1_MARKER'.