Fixes: 2879174 and 2879294. Also improves a bug to C3 and Google that made it so that attachments were displaying the wrong chart type.

This commit takes all sub-module-specific code out of the core charts module, making the module more extensible. It also improves the libraries.yml files and removes unused code from various parts of the site.

Charts can accept 'create secondary y-axis' option from Chart Attachment displays. This commit also removes a bug in Charts Google that led to duplicate empty fields.