The grib template manager is proving to be a reliable way for users to write non-standard gribs, like those in LAMs with custom grids and areas. To make this feature more user friendly:

• Improve documentation on how users can provide their own templates
• For the samples provider, add the option for the sample index to be specified directly in the inference config (right now it requires a separate yaml).
• For the file provider, add an option for the file to contain many parameters, and do a lookup based on the param name. We may also want an option to match the whole file against a lookup, but that use-case should already be covered by the samples provider.
• In the case of grib input, the template manager automatically injects templates found in the input grib. Refactor this so that this becomes its own standalone template provider, like input or from_input, this gives more flexibility to enable/disable combinations of template providers.
• Improve logging of the template manager. Right now it only logs in the case of errors. Also log in the case of success so it's easier to see which templates are being used from which provider.