String cast issue: field name is a graphql type and a reserved words in many languages

### Version Information

Server Version: 2.8.0
CLI Version (for CLI related issue): 2.8.0

### Environment

OSS

### What is the expected behaviour?

Fields in the graphql schema don't clash with graphql types and common reserved words in many languages.

### Keywords

cast, String, jsonb

### What is the current behaviour?

Schema contains fields named `String`. E.g.:
```
input jsonb_cast_exp {
String: String_comparison_exp
}
```

### How to reproduce the issue?

1. Export schema that uses jsonb, or any of the postgres types in https://github.com/hasura/graphql-engine/pull/8524

### Screenshots or Screencast

Error in autogenerated dart code for flutter app:


### Please provide any traces or logs that could help here.

Issue exists with JSONB since 2.5.0, but recently it was added to other types in this PR: https://github.com/hasura/graphql-engine/pull/8524

### Any possible solutions?

Use `string` or `_String`.

### Can you identify the location in the source code where the problem exists?

Not sure.

### If the bug is confirmed, would you be willing to submit a PR?

If someone can point me to the code, yes.

Start by reviewing pull request #8524 and the schema export path for JSONB and other PostgreSQL types. Reproduce the exported schema and inspect the generated Dart code; done means generated field names no longer collide with GraphQL types or common language reserved words.

Written by the indexing model from the issue text.