ENH: Simplify solving logic

This is a combination of multiple WIP commits:

- Semantic group names - G, H
- Simplify fan<>()
- Template int deduction
- Remove _recontext_gens
- Move g_gens logic into caller
- Move subgroup logic into caller
- Move recontext logic into coller
- Move _generators, _recontext_gens to anonymous namespace
- Simplify hull, tile

vis/src/main.cpp

@@ -140,14 +140,7 @@ int run(GLFWwindow* window, ImGuiContext* ctx) {
         entity,
         tc::schlafli({5, 3, 3, 2}),
         vec5{0.80, 0.09, 0.09, 0.09, 0.09},
-        vec3{0.90, 0.90, 0.90},
-        std::vector<std::vector<size_t>>{
-            {0, 1, 2},
-
-            {0, 3, 4},
-            {1, 3, 4},
-            {2, 3, 4},
-        }
+        vec3{0.90, 0.90, 0.90}
     );
     registry.emplace<vis::VBOs>(entity);