Adds support for instrumenting the AWS SDK for Java V2

[chrisradek]

Issue #, if available:
#43

Description of changes:
Adds 2 new artifacts for instrumenting the AWS SDK for Java V2.

The aws-xray-recorder-sdk-aws-sdk-v2 artifact exposes a TracingInterceptor class. An instance of this class can be passed into any AWS SDK V2 service client when it is being built:

DynamoDbAsyncClient client =  DynamoDbAsyncClient.builder()
    .region(Region.US_WEST_2)
    .overrideConfiguration(ClientOverrideConfiguration.builder()
        .addExecutionInterceptor(new TracingInterceptor())
        .build()
    ).build();

The aws-xray-recorder-sdk-aws-sdk-v2-instrumentor artifact allows for easy instrumentation of all AWS SDK V2 service clients. When included as a dependency, the AWS SDK will automatically inject the TracingInterceptor into each service client.

Both artifacts will require version 2.2.0 of the aws-sdk-java artifact in order to run.

I haven't dealt with maven-managed dependencies much. Currently, neither artifact will work unless the AWS SDK V2 is also a dependency of the consuming package. This allows the customer to specify which version of the AWS SDK they wish to use. If testing shows Maven will prefer the version of an artifact that is closest to the root pom.xml (and gradle works similarly) then it might make sense to explicitly depend on the AWS SDK in the new artifacts as well.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[haotianw465]

I looked up provided on Maven official doc but not quite clear what does this mean if user application specifies aws-sdk-java-bom with newer version or older version.

[dmytro-bekuzarov]

If I use Java SDK v2 only, I got the following error when I try to use AWSXRayServletFilter

java.lang.NoClassDefFoundError: com/amazonaws/services/xray/model/GetSamplingRulesRequest
	at com.amazonaws.xray.strategy.sampling.pollers.RulePoller.pollRule(RulePoller.java:64)
	at com.amazonaws.xray.strategy.sampling.pollers.RulePoller.lambda$start$0(RulePoller.java:46)

According to dependency tree, the x-ray sdk relies on AWS SDK 1.x version
Can it be used using Java SDK v2 only?
P.S. I see there is a module xray under software.amazon.awssdk, what's its current status?