Global Context for Load/Calculcations

[allenwyma]

Is your feature request related to a problem? Please describe.
When loading multiple resources, it'd be great to pass in a shared context to help alleviate complexity. I.E. a context for loading calculations.

Describe the solution you'd like
I'd like to be able to set the context: %{global: %{locale: "en"}}, and this will be merged with further context and available to me in calculations.

Describe alternatives you've considered
Right now, the alternative is I need to specifically set the query for the join relation, but this can be cumbersome if i'm joining a lot of resources.

Express the feature either with a change to resource syntax, or with a change to the resource interface

For example

Ash.read!(Post, load: [:name, comments: [:name], context: %{global: %{locale: "en"}})

Additional context
#1516