ENH: unify use of dictionary method names

- previously introduced `getOrDefault` as a dictionary _get_ method,
  now complete the transition and use it everywhere instead of
  `lookupOrDefault`. This avoids mixed usage of the two methods that
  are identical in behaviour, makes for shorter names, and promotes
  the distinction between "lookup" access (ie, return a token stream,
  locate and return an entry) and "get" access (ie, the above with
  conversion to concrete types such as scalar, label etc).

src/sampling/sampledSet/patchSeed/patchSeedSet.C

@@ -348,7 +348,7 @@ Foam::patchSeedSet::patchSeedSet
     maxPoints_(dict.get<label>("maxPoints")),
     selectedLocations_
     (
-        dict.lookupOrDefault<pointField>
+        dict.getOrDefault<pointField>
         (
             "points",
             pointField(0)