feat: throw when using both a template and a renderer #2098
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Description
Previously, all the components which had the public support of the Polymer Template API used to throw an exception when using both a template and a renderer. So far as it was a part of the Template API and we no longer support this API, it was decided that the Template Renderer should throw such exceptions instead.
This PR has a purpose to support throwing such exceptions for the Template Renderer.
Type of change
Checklist