Fix ObjC bridge generator for nested DataPoint types

[barboraplasovska]

What and why?

The ObjC interop code generator was walking all the way up to the top-level event class when resolving the root class for nested structs inside array items. This caused DataPoint wrapper classes to be typed as objc_RUMTimeseriesCpuEvent instead of objc_RUMTimeseriesCpuEventTimeseriesData, breaking the generated bridge.

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)
• Run make api-surface when adding new APIs

[barboraplasovska]

• Wire timeseries collection into RUM session and configuration #2885
• Add TimeseriesSessionCollector with memory and CPU collection #2884
• Add delta encoder for timeseries compression #2883
• Generate timeseries memory and CPU RUM event models #2882
• Fix ObjC bridge generator for nested DataPoint types #2881 👈 (View in Graphite)
• feature/timeseries

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