typescript-react-query: keep the possibility to define fetchParams when hardcoding the endpoint

`
config: {
fetcher: {
endpoint: '/api'
),
},
},
`
This removes the possibility to set fetchParams when using the generated code.

Start by tracing how the TypeScript React Query generator handles the fetcher configuration when an endpoint is hardcoded. Compare the generated configuration with the shown example and identify how fetchParams are currently lost. Done means fetchParams can still be defined alongside the hardcoded endpoint, with the relevant generator behavior covered by existing tests.

Written by the indexing model from the issue text.