Support aeson 2.0

In addition to the changes in #8355, supporting aeson 2.0 in `graphql-engine` would be all that's needed to allow building with the stackage LTS 19 solver. aeson 2.0 is mainly interesting as it mitigates a possible DoS related to JSON parsing.

From my testing all hasura-related packages except graphql-engine already build with aeson 2.0.

Start by reviewing the changes in issue #8355 and the graphql-engine build configuration for aeson constraints. Check the project with the Stackage LTS 19 solver and identify any remaining aeson 2.0 compatibility failures; done means graphql-engine builds successfully with that solver.

Written by the indexing model from the issue text.