Remove implicit conversion from string to Config

[AlwaysBlind]

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

The implicit conversion from string to Akka.Configuration.Config hides important intent and makes code less explicit. This can introduce subtle bugs where a plain string is unintentionally treated as a configuration object. It reduces readability and makes debugging harder, since the conversion is not obvious to readers or tools.

Describe the solution you'd like

Remove the implicit operator Config(string str) from the API. Users should explicitly call ConfigurationFactory.ParseString(str) when they want to create a Config instance. This makes intent clear and avoids unintentional type conversions.

Describe alternatives you've considered

1. Keeping the implicit operator but marking it [Obsolete] with a compiler warning, guiding developers to use ConfigurationFactory.ParseString explicitly.

2. Changing the operator to explicit instead of implicit, requiring an explicit cast in code but keeping backward compatibility.