STYLE: reduced usage of Switch

- Since 'bool' and 'Switch' use the _identical_ input mechanism
  (ie, both accept true/false, on/off, yes/no, none, 1/0), the main
  reason to prefer one or the other is the output.

  The output for Switch is as text (eg, "true"), whereas for bool
  it is label (0 or 1). If the output is required for a dictionary,
  Switch may be appropriate. If the output is not required, or is only
  used for Pstream exchange, bool can be more appropriate.

applications/utilities/mesh/generation/extrude/extrudeToRegionMesh/extrudeToRegionMesh.C

@@ -1536,8 +1536,8 @@ int main(int argc, char *argv[])
     mappedPatchBase::sampleMode sampleMode =
         mappedPatchBase::sampleModeNames_[dict.lookup("sampleMode")];
 
-    const Switch oneD(dict.lookup("oneD"));
-    Switch oneDNonManifoldEdges(false);
+    const bool oneD(dict.get<bool>("oneD"));
+    bool oneDNonManifoldEdges(false);
     word oneDPatchType(emptyPolyPatch::typeName);
     if (oneD)
     {
@@ -1545,7 +1545,7 @@ int main(int argc, char *argv[])
         dict.lookup("oneDPolyPatchType") >> oneDPatchType;
     }
 
-    const Switch adaptMesh(dict.lookup("adaptMesh"));
+    const bool adaptMesh(dict.get<bool>("adaptMesh"));
 
     if (hasZones)
     {