Add methods to query for template/file existence in run context

- Convenience methods added to CookbookVersion to query if a cookbook
  file or template is available for a given node in that cookbook
- Convenience methods added to RunContext to query the existence of
  cookbook files or templates
Remove deprecated method usage from package provider

Instead of using internal methods to trigger a template load and
rescuing the resulting error when a template is not found, query the run
context to determine if the cookbook has a given template.