Deprecate for removal protected access methods in converters

The protected method DateTimeStringConverter::getDateFormat was terminally deprecated in JavaFX 17 as part of JDK-8260475 and removed (by making it package-scope) in JavaFX 18 as part of JDK-8270838.

The getDateFormat method is overridden by the DateStringConverter and TimeStringConverter subclasses, and ideally should have been terminally deprecated and then removed at same time as the method in the base class.

We should correct that by terminally deprecating the overridden protected methods DateStringConverter::getDateFormat and TimeStringConverter::getDateFormat in JavaFX 22 and removing them (by making them package scope) in JavaFX 23.

I noticed this while looking at our existing javadoc warnings after bumping the warning limit to 1000. See JDK-8314590. Part of doing the deprecation should be to remove the now-erroneous "@inheritDoc" tag.

getNumberFormat() in NumberStringConverter (and subclasses) should also be terminally deprecated.