More verbose configure output to inform users about which XCB libraries are missing

If we run configure -xcb on the Qt 6.5 source code, we might get something like this:

ERROR: Feature "xcb": Forcing to "ON" breaks its condition:
    QT_FEATURE_thread AND TARGET XCB::XCB AND TEST_xcb_syslibs AND QT_FEATURE_xkbcommon_x11
Condition values dump:
    QT_FEATURE_thread = "ON"
    TARGET XCB::XCB found
    TEST_xcb_syslibs = "FALSE"
    QT_FEATURE_xkbcommon_x11 not evaluated

So we know that some XCB library/ies are missing, but there is no indication which ones (out of the very lengthy list at https://doc.qt.io/qt-6/linux-requirements.html) we need.

A customer struggled with this because they were so sure they had installed every possible XCB package on RHEL 8... but didn't realize that libxcb-cursor was in EPEL (similar to QTBUG-113647).

qtwebengine.git has a more detailed output (see QTBUG-120247), e.g.:

WARNING: QtWebEngine won't be built. Could not find all necessary libraries for qpa-xcb support. X11:YES LIBDRM:YES XCOMPOSITE:YES XCURSOR:NO XRANDR:YES XI:YES XPROTO:YES XSHMFENCE:YES XTST:YES

...would it be possible to do something similar in qtbase.git to provide more details on why "TEST_xcb_syslibs" failed? Perhaps only to be displayed if the -xcb option was provided?