Make classes related to page content parsing public

[BobLd]

The goal is to let BasePageFactory<T> decide the IPageContentParser implementation.

You can provide the IPageContentParser implementation as follow:

public sealed class PageFactoryWithoutIPageContentParser : BasePageFactory<int>
{
	public PageFactoryWithoutIPageContentParser(
		IPdfTokenScanner pdfScanner,
		IResourceStore resourceStore,
		ILookupFilterProvider filterProvider,
		IPageContentParser _, // Not in use
		ParsingOptions parsingOptions)
		: base(pdfScanner,
			resourceStore,
			filterProvider,
			new PageContentParser(ReflectionGraphicsStateOperationFactory.Instance, parsingOptions.UseLenientParsing), // Instantiate yours here
			parsingOptions)
	{
		if (PageContentParser is null)
		{
			throw new ArgumentNullException(nameof(PageContentParser));
		}
	}

	[...]
}