RUM-7691: Add addAttributes and removeAttributes APIs

[simaoseica-dd]

What and why?

This PR introduces a new interface to add and remove multiple attributes simultaneously.
This enhancement reduces threading pressure on the Message Bus when handling multiple attributes at once.

How?

The new interfaces to handle multiple attributes are:

func addAttributes(_ attributes: [AttributeKey: AttributeValue])

func removeAttributes(forKeys keys: [AttributeKey])

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
• Add CHANGELOG entry for user facing changes
• Add Objective-C interface for public APIs (see our guidelines [internal]) and run make api-surface)

[ncreated]

It's good direction and nice work on integration tests 👌🚀. I left a blocking feedback on the performance of attributes removal.

[datadog-datadog-prod-us1]

Datadog Report

Branch report: simaoseica/RUM-7691/add-addattributes-and-removeattributes-apis
Commit report: d1fa8ca
Test service: dd-sdk-ios

✅ 0 Failed, 1705 Passed, 2058 Skipped, 1m 47s Total duration (50.77s time saved)

[ncreated]

Well done! I appreciate the effort on adding coverage in Monitor+GlobalAttributes 🙂🏅.

[maxep]

It looks good, I've left a couple of minor suggestions 👍