feat: contribute xray lambda propagator

[yiyuan-he]

What does this pull request do?

Adding functionality to extract trace context in Lambda environments according to OTel propagator spec.

Usage:

require 'opentelemetry/sdk'
require 'opentelemetry/propagator/xray'

# Configure the OpenTelemetry SDK
OpenTelemetry::SDK.configure do |c|
  # Set propagator
  c.propagators = [OpenTelemetry::Propagator::XRay.lambda_text_map_propagator]
  # Other configuration...
end

Test plan

Set up a lambda function with lambda library instrumentation and new xray lambda propagator to verify the context propagation works.

Related Issues

#1462

[kaylareopelle]

Thank you!