Function argument aliases

### Is your proposal related to a problem?

We're currently unable to alias function arguments to be more ergonomic to consumers by matching existing field conventions.

For example:
- If i define a SQL function using camel case arguments, after creation the arguments will be lower case, which Hasura mirrors.
- If i define a SQL function using snake case arguments, then it is inconsistent with other Hasura fields i've exposed which follow camel case convention

### Describe the solution you'd like

Allow aliasing of function arguments (with the exception of the session argument), to create a more consistent public API

### Describe alternatives you've considered

Don't have any.

### If the feature is approved, would you be willing to submit a PR?

I don't think i have the Hasura expertise to pull this one off.

The issue names no files, tests, or entry points. Start by locating the code and tests responsible for exposing SQL function arguments through the GraphQL API, then determine how argument aliases should be represented and validated. Done means non-session function arguments can be aliased while preserving consistent public field names.

Written by the indexing model from the issue text.