Set the level for zstd best speed to 1 (elastic#125375)

This change sets the zstd best speed level from 0 to 1.
Compression level 0 means the default level will be used, which is level 3.
The intent of speed is to use the fastest compression level so 1 is a more appropriate value.
Note that zstd best speed is still under a feature flag so this change is just meant to evaluate the impact on our nightly benchmarks.
Further testing is needed (wip) to remove the feature flag entirely.

Author: jimczi

server/src/main/java/org/elasticsearch/index/codec/zstd/Zstd814StoredFieldsFormat.java

@@ -48,7 +48,7 @@ public final class Zstd814StoredFieldsFormat extends Lucene90CompressingStoredFi
     public static final String MODE_KEY = Zstd814StoredFieldsFormat.class.getSimpleName() + ".mode";
 
     public enum Mode {
-        BEST_SPEED(0, BEST_SPEED_BLOCK_SIZE, 128),
+        BEST_SPEED(1, BEST_SPEED_BLOCK_SIZE, 128),
         BEST_COMPRESSION(3, BEST_COMPRESSION_BLOCK_SIZE, 2048);
 
         final int level, blockSizeInBytes, blockDocCount;

server/src/test/java/org/elasticsearch/index/codec/CodecTests.java

@@ -57,7 +57,7 @@ public void testDefault() throws Exception {
         assumeTrue("Only when zstd_stored_fields feature flag is enabled", CodecService.ZSTD_STORED_FIELDS_FEATURE_FLAG.isEnabled());
         Codec codec = createCodecService().codec("default");
         assertEquals(
-            "Zstd814StoredFieldsFormat(compressionMode=ZSTD(level=0), chunkSize=14336, maxDocsPerChunk=128, blockShift=10)",
+            "Zstd814StoredFieldsFormat(compressionMode=ZSTD(level=1), chunkSize=14336, maxDocsPerChunk=128, blockShift=10)",
             codec.storedFieldsFormat().toString()
         );
     }