Add support for unit testing

* Downgraded macOS CI to Qt 6.2.0 due to a bug in Qt Test module
* Revised cmake build scripts
* For now, only building via cmake is supported

PR #17338.

test/CMakeLists.txt

@@ -0,0 +1,19 @@
+if (QT6)
+    find_package(Qt6 REQUIRED COMPONENTS Test)
+else()
+    find_package(Qt5 REQUIRED COMPONENTS Test)
+endif()
+
+enable_testing(true)
+add_custom_target(check COMMAND ${CMAKE_CTEST_COMMAND} --output-on-failure)
+
+include_directories("../src")
+
+file(GLOB testFiles "${CMAKE_CURRENT_SOURCE_DIR}/test*.cpp")
+foreach(testFile ${testFiles})
+    get_filename_component(testFilename "${testFile}" NAME_WLE)
+
+    add_executable("${testFilename}" "${testFile}")
+    target_link_libraries("${testFilename}" PRIVATE Qt::Test qbt_base)
+    add_test(NAME "${testFilename}" COMMAND "${testFilename}")
+endforeach()