feat: AWS X-Ray Remote Sampler Part 1 - Initial Classes and Rules Poller Implementation

[jj22ee]

Description

This is an initial PR to address #1434 in order for OTel Ruby to support X-Ray Remote Sampling. A series of PRs to fully implement this feature will follow this one.

Changes:

• Add new package directory sampler/xray/lib/opentelemetry-sampler-xray.rb
• Updated the OTel Contrib workflow to also run tests for this xray sampler gem
• Code changes:
  • Add Sampling Client class to communicate with X-Ray Service for Sampling Rules/Targets
  • Add X-Ray Sampling Rules/Statistics related classes to help represent the Sampling data from X-Ray
  • Added the AWSXRayRemoteSampler skeleton class
    • Ensure AWSXRayRemoteSampler is a ParentBased Sampler, with internal logic inside InternalAWSXRayRemoteSampler
    • Run poller upon instantiation to regularly obtain X-Ray Sampling Rules from X-Ray

Testing

• Unit Tests
• This PR is not a full implementation of the sampler, so it cannot be tested for correct x-ray sampling functionality.
  Right now, it currently always return a Parent Based decision or a DROP decision as a placeholder.
• A couple more PRs will follow-up to complete the implementation, which should look like this Sampler code from my fork. At that point in the future, a full E2E integration test will be run.

[jj22ee]

@kaylareopelle I've made the initial PR for X-Ray Sampler, will try to get someone from AWS who is familiar with X-Ray Sampling to help with the review.
Just not sure who can help review from OTel Ruby side since this is a new component.