Fix computation of last block size in Azure concurrent multipart uploads

Last part size is wrongly computed to 0 when the last
part's length is exactly equal to the size of a part.

Relates ES-11815

Author: tlrx

modules/repository-azure/src/main/java/org/elasticsearch/repositories/azure/AzureBlobStore.java

@@ -533,8 +533,9 @@ private static List<MultiPart> computeMultiParts(long totalSize, long partSize)
             return List.of(new MultiPart(0, makeMultipartBlockId(), 0L, totalSize, true));
         }
 
-        long lastPartSize = totalSize % partSize;
-        int parts = Math.toIntExact(totalSize / partSize) + (0L < lastPartSize ? 1 : 0);
+        long remaining = totalSize % partSize;
+        int parts = Math.toIntExact(totalSize / partSize) + (0L < remaining ? 1 : 0);
+        long lastPartSize = 0L < remaining ? remaining : partSize;
 
         long blockOffset = 0L;
         var list = new ArrayList<MultiPart>(parts);