### CI Link

- https://gradle-enterprise.elastic.co/s/tl3jqzmzqyktq (PR branch)
- https://gradle-enterprise.elastic.co/s/6ao6q7f42tsly (main)

### Repro line

./gradlew ':server:test' --tests "org.elasticsearch.index.mapper.vectors.DenseVectorFieldMapperTests.testVectorSimilarity" -Dtests.seed=39343A357A78EC3 -Dtests.locale=zh-CN -Dtests.timezone=Africa/Maseru -Druntime.java=21

### Does it reproduce?

Yes

### Applicable branches

main

### Failure history

_No response_

### Failure excerpt

  2> java.lang.AssertionError: expected:<COSINE> but was:<DOT_PRODUCT>
        at __randomizedtesting.SeedInfo.seed([39343A357A78EC3:75EC84B47EC59CF]:0)
        at org.junit.Assert.fail(Assert.java:88)
        at org.junit.Assert.failNotEquals(Assert.java:834)
        at org.junit.Assert.assertEquals(Assert.java:118)
        at org.junit.Assert.assertEquals(Assert.java:144)
        at org.elasticsearch.index.mapper.vectors.DenseVectorFieldMapperTests.testVectorSimilarity(DenseVectorFieldMapperTests.java:776)
server/src/test/java/org/elasticsearch/index/mapper/vectors/DenseVectorFieldMapperTests.java
e.getMessage(),
            containsString("Field [similarity] can only be specified for a field of type [dense_vector] when it is indexed")
        );
        e = expectThrows(
            MapperParsingException.class,
            () -> createDocumentMapper(INDEXED_BY_DEFAULT_PREVIOUS_INDEX_VERSION, fieldMapping(b -> {
                b.field("type", "dense_vector")
                    .field("dims", 3)
                    .startObject("index_options")
                    .field("type", "hnsw")
                    .field("m", 200)
                    .field("ef_construction", 20)
                    .endObject();
            }))
        );
        assertThat(
            e.getMessage(),
            containsString("Field [index_options] can only be specified for a field of type [dense_vector] when it is indexed")
        );
    }
    public void testDefaultParamsBeforeIndexByDefault() throws Exception {
        DocumentMapper documentMapper = createDocumentMapper(INDEXED_BY_DEFAULT_PREVIOUS_INDEX_VERSION, fieldMapping(b -> {
            b.field("type", "dense_vector").field("dims", 3);
        }));
        DenseVectorFieldMapper denseVectorFieldMapper = (DenseVectorFieldMapper) documentMapper.mappers().getMapper("field");
        DenseVectorFieldType denseVectorFieldType = denseVectorFieldMapper.fieldType();
        assertFalse(denseVectorFieldType.isIndexed());
        assertNull(denseVectorFieldType.getSimilarity());
    }
    public void testParamsBeforeIndexByDefault() throws Exception {