[Other] Fix all binding loops caused by misuse of bindable properties

Fix all properties that will fail the test implemented in QTBUG-116345.

In general case, the fix would be as simple as calling valueBypassingBindings() instead of simply accessing the property in the setter (see the epic for a code example).

The scope of this task is to implement fixes in all submodules that are not covered by the other tasks in the epic.

Using git-grep, I managed to get the following list of files in three submodules.
Qt Remote Objects

~/qt5/qtremoteobjects$ git grep -rI --name-only --recurse-submodules "Q_OBJECT_COMPAT_PROPERTY\|Q_OBJECT_COMPUTED_PROPERTY\|Q_OBJECT_BINDABLE_PROPERTY"
src/remoteobjects/qremoteobjectregistry.cpp

Qt Serial Port

~/qt5/qtserialport$ git grep -rI --name-only --recurse-submodules "Q_OBJECT_COMPAT_PROPERTY\|Q_OBJECT_COMPUTED_PROPERTY\|Q_OBJECT_BINDABLE_PROPERTY"
src/serialport/qserialport_p.h

Qt WebChannel

~/qt5/qtwebchannel$ git grep -rI --name-only --recurse-submodules "Q_OBJECT_COMPAT_PROPERTY\|Q_OBJECT_COMPUTED_PROPERTY\|Q_OBJECT_BINDABLE_PROPERTY"
src/webchannel/qmetaobjectpublisher_p.h
tests/auto/qml/testobject.h
tests/auto/webchannel/tst_webchannel.h

If it turns out that some of the classes are missing the tests for bindable properties, or if the tests do not use the QTestPrivate helpers, then the missing tests should be added.