Fielddata: Move getTermsEnum from AtomicFieldData to BytesValues.WithOrdinals.

Similarly to `SortedSetDocValues.termsEnum()`. Relates to elastic#6524

Author: jpountz

src/main/java/org/elasticsearch/index/fielddata/plain/AtomicFieldDataWithOrdinalsTermsEnum.java renamed to src/main/java/org/elasticsearch/index/fielddata/plain/BytesValuesWithOrdinalsTermsEnum.java

@@ -34,16 +34,16 @@
  * A general {@link org.apache.lucene.index.TermsEnum} to iterate over terms from a {@link AtomicFieldData.WithOrdinals}
  * instance.
  */
-public class AtomicFieldDataWithOrdinalsTermsEnum extends TermsEnum {
+public class BytesValuesWithOrdinalsTermsEnum extends TermsEnum {
 
  private final BytesValues.WithOrdinals bytesValues;
  private final long maxOrd;
 
  private long currentOrd = BytesValues.WithOrdinals.MISSING_ORDINAL;
  private BytesRef currentTerm;
 
- public AtomicFieldDataWithOrdinalsTermsEnum(AtomicFieldData.WithOrdinals afd) {
- this.bytesValues = afd.getBytesValues();
+ public BytesValuesWithOrdinalsTermsEnum(BytesValues.WithOrdinals bytesValues) {
+ this.bytesValues = bytesValues;
  this.maxOrd = bytesValues.getMaxOrd();
  }