Use OPTIONAL_COMPONENTS to search for KF5Wayland and DocTools

Summary:
Otherwise cmakes complains when invoked with
-DCMAKE_DISABLE_FIND_PACKAGE_KF5Wayland=TRUE: "CMake Error at
/usr/share/cmake/Modules/FeatureSummary.cmake:459 (message):
feature_summary() Error: REQUIRED package(s) are missing, aborting
CMake run."

Reviewers: KDE Connect

Tags: KDE Connect

Differential Revision: https://phabricator.kde.org/D12141