Avoid recursion in SideSetsGeneratorBase for fixed normal comparison

[dschwen]

Motivation

Recursion (or a custom stack) in this mesh generator is required to follow sides with progressively changing normals that are within tolerance of each other. It is not required for a fixed normal comparison, which should significantly improve performance for large meshes. Also there seems to be an unnecessary double loop over sides.

Design

Remove second (actually first) loop over the sides and bail early form flood for fixed normal comparison.

Impact

Improved performance, no stack overflow for large meshes.