Incorrect injection of builders in AWS service classes

## Description
It appears that the injection of the `IamClientBuilder`, `KinesisClientBuilder` and `CloudWatchLogsClientBuilder` in [Integrations AWS Service classes](https://github.com/Graylog2/graylog-plugin-integrations/blob/572efeda585a8061c4030794a1034f9c82db11bc/src/main/java/org/graylog/integrations/aws/service/) is currently being done incorrectly. In the current implementation, a single instance of the builders is injected and reused for each client creation. I suppose this has no actual symptoms (unless there is some edge case I am not seeing), since the config properties are re-written each time the client is instantiated.

See example in [CloudWatchService](https://github.com/Graylog2/graylog-plugin-integrations/blob/572efeda585a8061c4030794a1034f9c82db11bc/src/main/java/org/graylog/integrations/aws/service/CloudWatchService.java#L58)

See [here](https://github.com/Graylog2/graylog-plugin-integrations/blob/572efeda585a8061c4030794a1034f9c82db11bc/src/main/java/org/graylog/integrations/IntegrationsModule.java#L134) for the registration of the builders.

I suggest that the change the constructors to instead inject a `Provider<>` or factory class instead that creates a new builder each time one is needed instead of reusing the same one.