Java: Support struct scalar [skip ci]

[sperlingxx]

Current PR is to support struct scalar in Java package, which is required by spark-rapids (issue link). In detail, current PR introduces three new features:

1. create struct scalar through Java API
2. get children of struct scalar through Java API
3. create struct column from (struct) scalar through Java API

[sperlingxx]

Hi @revans2 @jlowe @firestarman, thanks for review!

I updated this PR, adding the support of ColumnVector.fromScalar on StructType (since #8310 merged).

[firestarman]

LGTM

[jlowe]

This won't do what we want. If an exception is thrown from the try block then this finally block will still clobber that exception if any close() call fails. It needs something like this:

  RuntimeException error = null;
  try {
    ...
  } catch (RuntimeException e) {
    error = e;
  } catch (Exception e) {
    error = new RuntimeException(e);
  } finally {
    for (ColumnVector child : children) {
      if (child != null) {
        try {
          child.close();
        } catch (Exception e) {
          if (error != null) {
            error.addSuppressed(e);
          } else {
            error = new RuntimeException(e);
          }
        }
      }
    }
    if (error != null) {
      throw error;
    }
  }

[sperlingxx]

Fixed. Thanks for the demo code!

[revans2]

This has the same problem as up above we need to not just eat the exceptions but add them to the suppression list.

[sperlingxx]

Fixed.

[sperlingxx]

@gpucibot merge