Improve ability to test and debug triangulation algorithm in Tessellator

While working on https://issues.apache.org/jira/browse/LUCENE-10563, it was found to be extremely difficult to debug the inner workings of the triangulation algorithm in the Tessellator class. To make things easier, we made use of a monitor interface that tests could use to instrument the algorithm and receive detailed information on the state of the algorithms progress. This issue requests that this interface and a test implementation of it be included in Lucene to facilitate future bug-fixing of this complex algorithm.