QVersionNumber: add missing size check for comparesEqual()

The whole point of separating comparesEqual() and compareThreeWay() is
that the former can fail faster than the latter.

To wit: segmentCount() is an inline operation and, for the common case
of SSO storage, a single byte read. compare(), OTOH, is an out-of-line
call.

So compare the segmentCount() before calling compare().

Amends ecb0878cbc3bc677d0f440950d2d1e304bcea495.

Change-Id: I3e46e73d4b8827532cc16428ca5e7f25bfa8608e
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
(cherry picked from commit 9bd3d39b3fe2d760b9c484663bdc6c863a68e22e)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/corelib/tools/qversionnumber.h

@@ -360,7 +360,7 @@ private:
     [[nodiscard]] friend bool comparesEqual(const QVersionNumber &lhs,
                                             const QVersionNumber &rhs) noexcept
     {
-        return compare(lhs, rhs) == 0;
+        return lhs.segmentCount() == rhs.segmentCount() && compare(lhs, rhs) == 0;
     }
     [[nodiscard]] friend Qt::strong_ordering compareThreeWay(const QVersionNumber &lhs,
                                                              const QVersionNumber &rhs) noexcept