Increase blob container max register content length (elastic#127701)

Allowing a bit more space than elastic#127491, for the same purposes.

Relates ES-11205

Author: pxsalehi

server/src/main/java/org/elasticsearch/common/blobstore/support/BlobContainerUtils.java

@@ -22,7 +22,7 @@ private BlobContainerUtils() {
         // no instances
     }
 
-    public static final int MAX_REGISTER_CONTENT_LENGTH = 3 * Long.BYTES;
+    public static final int MAX_REGISTER_CONTENT_LENGTH = 4 * Long.BYTES;
 
     public static void ensureValidRegisterContent(BytesReference bytesReference) {
         if (bytesReference.length() > MAX_REGISTER_CONTENT_LENGTH) {

server/src/test/java/org/elasticsearch/common/blobstore/fs/FsBlobContainerTests.java

@@ -237,7 +237,7 @@ public void testCompareAndExchange() throws Exception {
             expectedValue.set(newValue);
         }
 
-        container.writeBlob(randomPurpose(), key, new BytesArray(new byte[25]), false);
+        container.writeBlob(randomPurpose(), key, new BytesArray(new byte[33]), false);
         assertThat(
             safeAwaitFailure(
                 OptionalBytesReference.class,