Tests in non-qtbase modules could not find_package their own Qt6*Tools
packages, because add_subdirectory(tests) was called before the config
files for Qt6*Tools were created.
The creation of tools config files is done in QtPostProcess.cmake, which
was included in qt_build_repo_end(). Move that include into its own
macro, qt_build_repo_post_process() and remove it from
qt_build_repo_end(). Call qt_build_repo_post_process() before the
'tests' directory is added in qt_build_repo().
Every call site of qt_build_repo_end() must now be adjusted and call
qt_build_repo_post_process().
Task-number: QTBUG-88264
Change-Id: I80d60a1b5c0e9b715c298ef4934b562f815432d1
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
