Add Traceparent to Outgoing Requests

[dvernon-splunk]

Adds the traceparent to the header of outgoing HTTP requests.

Unfortunately, the request object is get-only where we were creating spans, requiring us to swizzle the task functions in URLSessionTask. This solution was adapted, and heavily modified, from opentelemetry-swift: https://github.com/open-telemetry/opentelemetry-swift/blob/8d6fa745c186e3b7556f330b5236da25fa7c9d62/Sources/Instrumentation/URLSession/URLSessionInstrumentation.swift

The proposed solution swizzles urlsession tasks that take in (or requests) a request object, and passes through a modified request object with the added traceparent header.

Also includes a new variable in SplunkRumOptions, allowing users to enable. It is false by default.

[dvernon-splunk]

Found an issue while debugging the failing unit test: Do not review yet.

[dvernon-splunk]

The unit tests are still failing, but I wanted to get this proposed solution in before I leave for vacation. The data task unit test succeeds if you run it by itself. If this direction is something we're good with, I will fix the unit tests (and bugs, and lint errors) when I return.

[github-actions]

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1 out of 2 committers have signed the CLA.
✅ (seemk)[https://github.com/seemk]
❌ @dvernon-splunk
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