RUMM-1583 Fix attributes reading in Objective-C

[ncreated]

What and why?

📦 This PR fixes DatadogObjc issue with retrieving back attribute values in public APIs.

It was not possible to obtain the value of Any attribute, i.e. this would fail:

let view = DDRUMView(name: "name", attributes: ["foo": "bar"])
XCTAssertEqual(view.attributes["foo"] as? String, "bar") // 🐞 fail

It would fail because "bar" is wrapped into AnyEncodable(value: "bar") type erasure as part of our Objective-C <> Swift interoperability (Swift SDK represents attributes as Encodable). AnyEncodable is internal type to DatadogObjc so it was not even possible to read the attribute value back in any other way.

How?

I introduced func castAttributesToObjectiveC(_ attributes: [String: Encodable]) -> [String: Any] function to unpack AnyEncodable values before they are passed to the user.

This had to be used in DDRUMView, DDRUMAction and all generated RUMDataModels for Objective-C.

Now, users will get exactly what they set through our Objective-C API.

Review checklist

• Feature or bugfix MUST have appropriate tests (unit, integration)
• Make sure each commit and the PR mention the Issue number or JIRA reference

[maxep]

👍