add score-less (abstract) DocTransformer.transform method

Background and motivation:

• Most DocTransformer implementations don't use the score argument of the transform method.

• Two-and-a-half of the three method callers pass 0 to indicate "no score".
  • https://github.com/apache/lucene-solr/blob/releases/lucene-solr/6.6.0/solr/core/src/java/org/apache/solr/handler/component/RealTimeGetComponent.java#L253
  • https://github.com/apache/lucene-solr/blob/releases/lucene-solr/6.6.0/solr/core/src/java/org/apache/solr/handler/component/RealTimeGetComponent.java#L302
  • https://github.com/apache/lucene-solr/blob/releases/lucene-solr/6.6.0/solr/core/src/java/org/apache/solr/response/DocsStreamer.java#L170

• Without the change being proposed in this ticket the fix for SOLR-11180 and SOLR-11220 (included in the SOLR-11164 patch) would need to also interpret a score of 0 to mean "no score".

Summary of proposed change (for master and branch_7x branches):

-  public abstract void transform(SolrDocument doc, int docid, float score) throws IOException;
+  public void transform(SolrDocument doc, int docid, float score) throws IOException {
+    transform(doc, docid);
+  }
+
+  public abstract void transform(SolrDocument doc, int docid) throws IOException;