Replace the monolithic RigNonUniformRefinement class with a proper
polymorphic hierarchy: RigRefinement (abstract base), RigNoRefinement
(identity), RigUniformRefinement (O(1) uniform), and
RigNonUniformRefinement (per-cell custom fractions).
Ownership uses std::unique_ptr<RigRefinement>, consumers receive
const RigRefinement&. This eliminates the misleading class name,
removes effectiveRefinement() indirection, and gives each refinement
mode an appropriately optimized implementation.
Add effectiveRefinement() to RicRefinementSettings, RicExportSectorModelUi, and
RigSimulationInputSettings, always returning RigNonUniformRefinement regardless of
whether uniform, non-uniform, or no refinement is active.
Merge the dual RigGridExportAdapter constructors into a single one taking
RigNonUniformRefinement, and unify transformIjkToSectorCoordinates to a single
overload. Eliminate all hasNonUniformRefinement() branching patterns in
RigSimulationInputTool.cpp in favour of effectiveRefinement().
Add refined grid border detection for BCCON_BCPROP boundary conditions.
The refined functions operate on the exported refined grid dimensions,
ensuring border cells are correctly identified when using grid refinement.