Change file exist exception to runtime exception in PagedDoraWorker

### What changes are proposed in this pull request?

The `RuntimeException(FileAlreadyExistException)` changed to `AlreadyExistException()` in `PagedDoraWorker`

### Why are the changes needed?

`RuntimeException(FileAlreadyExistException)` seems won't be caught in `DoraWorkerClientServiceHandler` when convertin it to `AlluxioRuntimeException`, which willl cause the loss status code

### Does this PR introduce any user facing changes?

no

			pr-link: Alluxio#18337
			change-id: cid-9a520c49579847bae6da21302f484ba713eeb4d9

dora/core/server/worker/src/main/java/alluxio/worker/dora/PagedDoraWorker.java

@@ -32,10 +32,10 @@
 import alluxio.conf.Configuration;
 import alluxio.conf.PropertyKey;
 import alluxio.exception.AccessControlException;
-import alluxio.exception.FileAlreadyExistsException;
 import alluxio.exception.runtime.AlluxioRuntimeException;
 import alluxio.exception.runtime.FailedPreconditionRuntimeException;
 import alluxio.exception.runtime.UnavailableRuntimeException;
+import alluxio.exception.status.AlreadyExistsException;
 import alluxio.exception.status.FailedPreconditionException;
 import alluxio.grpc.Command;
 import alluxio.grpc.CommandType;
@@ -879,9 +879,8 @@ public OpenFileHandle createFile(String path, CreateFilePOptions options)
       boolean overWrite = options.hasOverwrite() ? options.getOverwrite() : false;
       boolean exists = ufs.exists(path);
       if (!overWrite && exists) {
-        throw new RuntimeException(
-            new FileAlreadyExistsException(
-                String.format("File %s already exists but no overwrite flag", path)));
+        throw new AlreadyExistsException(String.format("File %s already exists"
+            + "but no overwrite flag", path));
       } else if (overWrite) {
         // client is going to overwrite this file. We need to invalidate the cached meta and data.
         mMetaManager.removeFromMetaStore(path);
@@ -1010,11 +1009,11 @@ public void createDirectory(String path, CreateDirectoryPOptions options)
       mMetaManager.loadFromUfs(path);
       mMetaManager.invalidateListingCacheOfParent(path);
       if (!success) {
-        throw new RuntimeException(
-            new FileAlreadyExistsException(String.format("%s already exists", path)));
+        throw new AlreadyExistsException(String.format("%s already exists", path));
       }
     } catch (IOException e) {
-      throw new RuntimeException(e);
+      // IOE would be caught by AlluxioRuntimeException
+      throw e;
     }
   }
 

dora/tests/integration/src/test/java/alluxio/client/cli/fs/command/DoraMkdirCommandIntegrationTest.java

@@ -51,7 +51,7 @@ public void testMkdirExisting() {
     assertEquals(0, mFsShell.run("mkdir", uri.toString()));
     assertEquals(-1, mFsShell.run("mkdir", uri.toString()));
     assertTrue(
-        mOutput.toString().contains("UNKNOWN: alluxio.exception.FileAlreadyExistsException"));
+        mOutput.toString().contains("ALREADY_EXISTS"));
   }
 
   @Test
@@ -76,7 +76,7 @@ public void testMkdirPathWithWhiteSpaces() throws Exception {
   public void testMkdirInvalidPath() {
     assertEquals(-1, mFsShell.run("mkdir", ""));
     assertTrue(
-        mOutput.toString().contains("UNKNOWN: alluxio.exception.FileAlreadyExistsException"));
+        mOutput.toString().contains("ALREADY_EXISTS"));
   }
 
   @Test