Re-export functions useful to modelers from `hubUtils` and `hubData`

[annakrystalli]

In a recent PR in hubDocs on model output data addressed heavily towards modelers, a number of useful functions were suggested which were spread over 3 different packages:

• hubUtils::read_config()
• hubData::create_hub_schema() and hubData::coerce_to_hub_schema()
• hubValidations::submission_tmpl()

While there's good reason for the original functions to be spread out across these packages, I feel hubValidations is really the package with modelers as a key target and therefore should contain any functions required for their workflows. As such, I propose we re-export the above functions from other packages into hubValidations so they are available to modelers through this package.

hubUtils and hubData are already imports to hubValidations so it should be an easy fix.

[zkamvar]

I think this is a good idea and will implement.