ENH: consolidate 'formatOptions' handling for coordSetWriter/surfaceWriter

- replaced ad hoc handling of formatOptions with coordSetWriter and
  surfaceWriter helpers.

  Accompanying this change, it is now possible to specify "default"
  settings to be inherited, format-specific settings and have a
  similar layering with surface-specific overrides.

- snappyHexMesh now conforms to setFormats

  Eg,

      formatOptions
      {
          default
          {
              verbose     true;
              format      binary;
          }
          vtk
          {
              precision   10;
          }
     }

     surfaces
     {
         surf1
         {
             ...

             formatOptions
             {
                 ensight
                 {
                     scale   1000;
                 }
             }
         }
     }

src/functionObjects/forces/propellerInfo/propellerInfo.C

@@ -355,16 +355,20 @@ void Foam::functionObjects::propellerInfo::setSampleDiskSurface
         points_
     );
 
-    // Surface writer
-    word surfWriterType;
-    if (sampleDiskDict.readIfPresent("surfaceWriter", surfWriterType))
-    {
-        const auto writeOptions = sampleDiskDict.subOrEmptyDict("writeOptions");
+    // Surface writer (keywords: surfaceWriter, writeOptions)
 
+    word writerType;
+    if (sampleDiskDict.readIfPresent("surfaceWriter", writerType))
+    {
         surfaceWriterPtr_ = surfaceWriter::New
         (
-            surfWriterType,
-            writeOptions.subOrEmptyDict(surfWriterType)
+            writerType,
+            surfaceWriter::formatOptions
+            (
+                sampleDiskDict,
+                writerType,
+                "writeOptions"
+            )
         );
 
         // Use outputDir/TIME/surface-name