The following aggregation tests all contain switch statements with branches that will never execute. The tests use a `between(x, y)` switch expression, but there are `case` values that are outside the randomised range. We need to fix these before #88739 can be merged. By "fix", I mean either remove the spurious cases, or if we actually want them, then extend the randomized range.

   * InternalAutoDateHistogramTests
   * InternalAvgTests
   * InternalDerivativeTests
   * InternalGeoCentroidTests
   * InternalWeightedAvgTests
   * SignificantLongTermsTests
   * SignificantStringTermsTests
server/src/test/java/org/elasticsearch/search/aggregations/bucket/terms/SignificantStringTermsTests.java
format,
                subsetSize,
                supersetSize,
                significanceHeuristic,
                buckets
            );
        } else {
            String name = instance.getName();
            int requiredSize = instance.requiredSize;
            long minDocCount = instance.minDocCount;
            Map<String, Object> metadata = instance.getMetadata();
            switch (between(0, 3)) {
                case 0 -> name += randomAlphaOfLength(5);
                case 1 -> requiredSize += between(1, 100);
                case 2 -> minDocCount += between(1, 100);
                case 3 -> {
                    if (metadata == null) {
                        metadata = Maps.newMapWithExpectedSize(1);
                    } else {
                        metadata = new HashMap<>(instance.getMetadata());
                    }
                    metadata.put(randomAlphaOfLength(15), randomInt());
                }
                default -> throw new AssertionError("Illegal randomisation branch");
            }
            return new UnmappedSignificantTerms(name, requiredSize, minDocCount, metadata);
        }
    }
}