[near-operation-file] Option to generate files based on operation name, not component name

**Is your feature request related to a problem? Please describe.**

Some tools such as [Apollo Tooling](https://github.com/apollographql/apollo-tooling) generate files based on operation name.

**Describe the solution you'd like**

To make it easier [to migrate from Apollo Tooling to Codegen](https://github.com/apollographql/apollo-tooling/issues/2053), we could have an option to generate file name based on operation names.

## Examples

```
// GraphQL Codegen detects gql in a React component:
------- ReactComponent.ts
...
const GET_FOO_QUERY = gql`
query GetFoo($id: String) {
...
}
`;
...
=========

// BEFORE: the generated filename is always based on the React component's filename:
------- ./__generated__/ReactComponent.ts
...
export type GetFooVariables = ...

export type GetFoo = ...
...
========

// AFTER: add a configuration option so the generated filename is based on the operation name (Query, Mutation, or Fragment):
------- ./__generated__/GetFoo.ts
...
export type GetFooVariables = ...

export type GetFoo = ...
```