Fixes#8104.
As described in that issue, a crash happens under the following
conditions:
1. A `DrawSketchHandler` is active.
2. No constraint is selected.
3. Context menu on the `ConstraintView` is triggered.
* QString::indexOf() is now marked as [[nodiscard]]
* QApplication::fontMetrics() is deprecated, use the constructor of QFontMetricsF
* fix -Wunused-result
* fix -Wunused-but-set-variable
* ignore -Wfree-nonheap-object for generated code
* replace 0 with Qt::NoModifier when creating a QKeyEvent
* in Qt 5.14 QCombobox::activated(QString) is deprecated, use textActivated
* don't mix QCheckBox::setChecked() with tristate API
* Missing reference in range-for with non trivial type [-Wclazy-range-loop-reference]
* Unused QString [-Wclazy-unused-non-trivial-variable]
* Missing emit keyword on signal call [-Wclazy-incorrect-emit]
* Don't call QList::operator[]() on temporary [-Wclazy-detaching-temporary]
* Use multi-arg instead [-Wclazy-qstring-arg]
* Maybe you meant to call ViewProvider2DObjectGrid::onChanged() instead [-Wclazy-skipped-base-method]
===================================================
This commit is an independent refactor of the identifications used at Sketcher level.
It introduces a new type "GeoElementId" as a combination of GeoId and PointPos.
It moves the Undefined GeoId, previous Constraint::GeoUndef to GeoEnum, together with all
other fixed values of GeoIds.
=================================================================
Common utility functions used by almost all Command classes were previous in Constraint.h.
Aside from providing a very bad intent, it created unnecessary header dependencies.
This commit separates these common functions into a new header, utils.h, which is then
used in all command classes where it is necessary.
