fix: issue with sending traces to IPv6 endpoints

[chen-anders]

Resolves: https://github.com/open-telemetry/opentelemetry-ruby/issues/1721

This PR resolves the issue around using the opentelemetry-ruby SDK for apps that send traces to an IPv6 endpoint using the suggested fix in the original issue. We also add some tests for verifying the expected value of the collector hostname based on a passed-in value.

Reviewer's Note: Tests were written with significant AI assistance.

[github-actions[bot]]

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