Handle unknown fields in sampler APIs response

[srprash]

Issue # : #423
Even though the issue is closed due to mitigation by rollback, the problem is with the deserialization of response in the SDK.

Description of changes:

• Configuring the Jackson's deserialization to NOT fail on unknown fields.
  • For reference, OTel XRay Sampler already does the configuration for this specific purpose: https://github.com/open-telemetry/opentelemetry-java-contrib/blob/a8338679e7d3e74e5aa7a5845198695aa423929e/aws-xray/src/main/java/io/opentelemetry/contrib/awsxray/XraySamplerClient.java#L58-L59

Testing:

• Without the configuration, the UnsignedXrayClientTest > getSamplingTargets unit test fails with the following error:

  com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "Foo" (class com.amazonaws.services.xray.model.SamplingTargetDocument), not marked as ignorable (5 known properties: "ReservoirQuota", "ReservoirQuotaTTL", "FixedRate", "Interval", "RuleName"])
  at [Source: (sun.net.www.protocol.http.HttpURLConnection$HttpInputStream); line: 9, column: 21] (through reference chain: com.amazonaws.services.xray.model.GetSamplingTargetsResult["SamplingTargetDocuments"]->java.util.ArrayList[0]->com.amazonaws.services.xray.model.SamplingTargetDocument["Foo"])

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