Implement error handling option: "results" | "exceptions" for the fsharp target

[Zaid-Ajaj]

Right now, the client methods generated per query come in two flavors and both return Result:

• Asynchronous call returns Async<Result<Query, ErrorType list>>
• Synchronous call returns Result<Query, ErrorType list>

Sometimes, using result can be tricky where users don't necessarily care about handling errors each request. A try-catch block might more suitable.

To improve the situation, add an option

{
  ["errorHandling"]: < "results" | "exceptions" >
}

where results is the default. When exceptions is used then the generated functions will use exceptions for error handling instead

• Asynchronous call returns Async<Query>
• Synchronous call returns Query

An exception type is generated

exception GraphqlError of ErrorType list

which is thrown when the GraphQL backend returns a non-OK response

[xperiandri]

I don't think it is necessary