[BEAM-7813] FileIO.write() doesn't fail when writing to invalid bucket

`writer` shouldn't be closed in `flush()` otherwise FileIO.write()
doesn't fail when writing to unhealthy channel. It's safe to just
`flush` instead of `close` because channel is closed after writing
in the parent scope anyway.

sdks/java/core/src/main/java/org/apache/beam/sdk/io/TextIO.java

@@ -1318,7 +1318,8 @@ public void flush() throws IOException {
  if (getFooter() != null) {
  writer.println(getFooter());
  }
- writer.close();
+ // BEAM-7813: don't close writer here
+ writer.flush();
  }
  }
 

sdks/java/io/parquet/src/main/java/org/apache/beam/sdk/io/parquet/ParquetIO.java

@@ -316,6 +316,7 @@ public void write(GenericRecord element) throws IOException {
 
  @Override
  public void flush() throws IOException {
+ // the only way to completely flush the output is to call writer.close() here
  writer.close();
  }
 

sdks/java/io/xml/src/main/java/org/apache/beam/sdk/io/xml/XmlIO.java

@@ -680,6 +680,7 @@ public void write(T element) throws IOException {
  @Override
  public void flush() throws IOException {
  outputStream.write(("\n</" + getRootElement() + ">").getBytes(Charset.forName(getCharset())));
+ outputStream.flush();
  }
  }
 }