StatelessSession insertAll in batch does not do batching

[dreab8]

Fix #2108

[dreab8]

Unfortunately with this change it works but only in conjunction with hibernate.jdbc.batch_size > 1.
I'm working on a change that should allow insertAll(int batchSize, Object... entities) to respect the batchSize even when hibernate.jdbc.batch_size is not set.

[gavinking]

@dreab8 you see how I did it in ORM, right?

	@Override
	public void insertMultiple(List<?> entities) {
		final Integer batchSize = getJdbcBatchSize();
		setJdbcBatchSize( entities.size() );
		try {
			for ( Object entity : entities ) {
				insert( null, entity );
			}
		}
		finally {
			setJdbcBatchSize( batchSize );
		}
	}

[dreab8]

In reactive we need also to use a BatchingConnection and at the moment if batcSize <2 we use the original connection also for the batchingHelperSession

Preparing a PR.

[dreab8]

@gavinking #2136

[dreab8]

superseeded by #2136