Summary data improvements

[magnesj]

There is a lot of common features shared between a RimSummaryCurve and RimEnsembleCurveSet

• available addresses
• available time steps
• axis management
• resampling

A lot of code is duplicated, and I suggest improving the design in the following way

• create an implementation of RifSummaryReaderInterface that can work with RimSummaryCaseCollection
  See class RimEnsembleStatisticsCase : public RimSummaryCase, public RifSummaryReaderInterface
• establish a common base class with working name RimSummaryBase for RimSummaryCurve and RimEnsembleCurveSetInterface
• use RimSummaryBase where possible in RimSummaryPlot

Comments
If we add support for realization number to RifSummaryReaderInterface, we can use this as a base class for ensemble data.

Consider if it can be useful to move common operations into a visitor pattern. https://github.com/igl42/cpp_software_design/blob/main/G17_Visitor.cpp