Bindings in catch/finally blocks of computation expressions

[Horusiath]

I propose we add support for bindings in catch/finally blocks of computations expressions, eg.:

let doWork () = task {
   try
     return! doSomething ()
   finally
     do! doSomethingElse()   // this is not supported by the compiler right now
}

Another related problem is that there's no equivalent of C# await using and in current state of the compiler it's impossible to create non-blocking one by yourself, as IAsyncDisposable would require bind in a finally block (see above).

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[dsyme]

Approving this. We should look for a method such as TryFinallyMonadic or similar (not sure of the best name, it doesn't matter too much) and use that with the richer signature.

[jwosty]

Isn't this essentially the same as #651?