- added new `QString QgsField::displayType( const bool showConstraints = false )` to unify the display of field types whenever length or precision are present
- added new argument `expression` to `QgsFieldModel::fieldToolTip( const QgsField &field, const QString &expression = QStringLiteral() )`. Now the tooltip shows "<alias> (<field>)\n<type>\n<comment>\n<expression>" with appropriate formatting
- added meaningful field tooltips in the "Identify Results" dialog
- field tooltips show the same content in "Feature Attributes" form, "Attribute Table" and "Identify Tool"
Fixes#15144