Remove compaction final state from code and in upgrade step

[keith-turner]

After #3460 the compaction final state metadata was no longer needed. This can be removed from the metadata schema and ample. Also an upgrade step should be added that removes it from the metadata table.

Below is some of the code that needs to be removed.

accumulo/core/src/main/java/org/apache/accumulo/core/metadata/schema/MetadataSchema.java

Line 418 in 447b2e5

public static class ExternalCompactionSection {

accumulo/core/src/main/java/org/apache/accumulo/core/metadata/schema/Ample.java

Lines 205 to 215 in 447b2e5

	putExternalCompactionFinalStates(Collection<ExternalCompactionFinalState> finalStates) {
	throw new UnsupportedOperationException();
	}
	default Stream<ExternalCompactionFinalState> getExternalCompactionFinalStates() {
	throw new UnsupportedOperationException();
	}
	default void
	deleteExternalCompactionFinalStates(Collection<ExternalCompactionId> statusesToDelete) {
	throw new UnsupportedOperationException();