ENH: eliminate reliance on SLList during reading

- fully implement DynamicList::readList() instead of simply
  redirecting to List::readList(). This also benefits DynamicField.
  Leverage DynamicList reading to simplify and improve CircularBuffer
  reading.

- bracket lists are now read chunk-wise instead of using a
  singly-linked list. For integral and vector-space types
  (eg, scalar, vector, etc) this avoids intermediate allocations
  for each element.

ENH: add CircularBuffer emplace_front/emplace_back

STYLE: isolate to-be-deprecated construct/assign forms

- still have construct/assign FixedList from a C-array.
  This is not really needed, can use std::initializer_list

- still have construct/assign List from SLList.
  Prefer to avoid these in the future.

DEFEATURE: remove construct/assign FixedList from SLList

- never used

DEFEATURE: remove move construct/assign List from SLList

- now unused. Retain copy construct/assign from SLList for transition
  purposes.

applications/test/FixedList/Test-FixedList.C

@@ -202,14 +202,31 @@ int main(int argc, char *argv[])
         Info<< "get<3>: " << list1.get<3>() << nl;
 // Will not compile:  Info<< "get<4>: " << list1.get<4>() << nl;
 
-        label a[4] = {0, 1, 2, 3};
-        FixedList<label, 4> list2(a);
+        // Test deprecated form
+        label array2[4] = {0, 1, 2, 3};
+        FixedList<label, 4> list2(array2);
 
         Info<< "list2:" << list2
             << " hash:" << FixedList<label, 4>::hasher()(list2) << nl
             << " hash:" << Hash<FixedList<label, 4>>()(list2) << nl;
 
 
+        // Test deprecated form
+        SLList<label> sllist3;
+        {
+            sllist3.push_back(0);
+            sllist3.push_back(1);
+            sllist3.push_back(2);
+            sllist3.push_back(3);
+        }
+        FixedList<label, 4> list3(sllist3);
+
+        Info<< "list3:" << list3 << nl;
+        // Test deprecated forms
+        list3 = array2;
+        list2 = sllist3;
+
+
         // Using FixedList for content too
         {
             List<FixedList<label, 4>> twolists{list1, list2};