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/histogram/InternalAutoDateHistogramTests.java
buckets.add(
                    new InternalAutoDateHistogram.Bucket(
                        randomNonNegativeLong(),
                        randomIntBetween(1, 100),
                        instance.getFormatter(),
                        InternalAggregations.EMPTY
                    )
                );
            }
            case 2 -> {
                int roundingIdx = bucketInfo.roundingIdx == bucketInfo.roundingInfos.length - 1 ? 0 : bucketInfo.roundingIdx + 1;
                bucketInfo = new BucketInfo(bucketInfo.roundingInfos, roundingIdx, bucketInfo.emptySubAggregations);
            }
            case 3 -> {
                if (metadata == null) {
                    metadata = Maps.newMapWithExpectedSize(1);
                } else {
                    metadata = new HashMap<>(instance.getMetadata());
                }
                metadata.put(randomAlphaOfLength(15), randomInt());
            }
            case 4 -> interval = randomNonNegativeLong();
            default -> throw new AssertionError("Illegal randomisation branch");
        }
        return new InternalAutoDateHistogram(name, buckets, targetBuckets, bucketInfo, instance.getFormatter(), metadata, interval);
    }
    public void testReduceSecond() {
        InternalAutoDateHistogram h = new ReduceTestBuilder(10).bucket("1970-01-01T00:00:01", 1)
            .bucket("1970-01-01T00:00:02", 1)
            .bucket("1970-01-01T00:00:03", 1)