Support AWS SDK V2

You can find the current AWS SDK V2 progress in the branch aws-v2:
https://github.com/dibog/cloudwatch-logback-appender/tree/aws-v2

The binaries can be found here:
```
<dependency>
    <groupId>io.github.dibog</groupId>
    <artifactId>cloudwatch-logback-appender</artifactId>
    <version>2.0.0</version>
</dependency>
```