Disabling Chunked Encoding

### What happened?
Currently responses received always have `Transfer-Encoding: chunked`

### What did you expect?
I wish to control this and send complete response.

### Minimal graphql.schema and models to reproduce
Not specific to a schema

### versions
```
go run github.com/99designs/gqlgen version
v0.17.36
go version
go version go1.19.3 darwin/arm64
```

Look at the HTTP transport layer in gqlgen, likely in handler or transport packages, to find where Transfer-Encoding: chunked is set. Understand how to conditionally disable chunked encoding based on request or response size. Check existing tests for HTTP handlers to see how responses are validated.

Written by the indexing model from the issue text.