RUM-4315 feat: Add missing RUM APIs for Objective-C

[ncreated]

What and why?

📦 This PR adds missing RUM APIs for Objective-C SDK.

How?

The list includes:

• [monitor currentSessionIDWithCompletion:]
• [monitor stopSession]
• [monitor addFeatureFlagEvaluationWithName:value:]
• [monitor setDebug:]

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

Custom CI job configuration (optional)

• Run unit tests for Core, RUM, Trace, Logs, CR and WVT
• Run unit tests for Session Replay
• Run integration tests
• Run smoke tests
• Run tests for tools/

[datadog-datadog-prod-us1]

Datadog Report

Branch report: ncreated/RUM-4315/add-missing-objc-apis-for-rum
Commit report: ed9ab00
Test service: dd-sdk-ios

✅ 0 Failed, 2905 Passed, 0 Skipped, 2m 12.6s Total Time
🔻 Test Sessions change in coverage: 4 decreased, 4 increased, 5 no change

🔻 Code Coverage Decreases vs Default Branch (4)

• test DatadogCrashReportingTests tvOS 27.64% (-0.07%) - Details
• test DatadogCrashReportingTests iOS 27.61% (-0.05%) - Details
• test DatadogTraceTests tvOS 55.6% (-0.03%) - Details
• test DatadogInternalTests tvOS 80% (-0.02%) - Details

[maciejburda]

LGTM!