[core] Give user the possibility to pass their logger to the lambda runtime

[sebsto]

Allow user to give their logger to the LambdaRuntime.

Motivation:

Overloaded versions of LambdaRuntime.init don't allow to pass a logger

Modifications:

Add a logger parameter to overloaded versions of LambdaRuntime.init

Result:

It is now possible to write

        let runtime = LambdaRuntime(logger: Logger(label: "MyLogger"), body: handler)