What and why?

Add a public version configuration parameter to allow native iOS applications to explicitly set their app version for Unified Service Tagging. This addresses the need to identify TestFlight builds with specific build numbers (e.g., 1.0.0-1234) for better correlation of logs and errors in Datadog.

Previously, developers had to use undocumented internal APIs like DatadogCore.set(customVersion:) or cross-platform-specific configuration, both of which are unsupported for native iOS use.

Fixes #2585

How?

• Added optional version property to both Datadog.Configuration (Swift) and objc_Configuration
  (Objective-C)
• Updated version resolution logic in Datadog.swift with clear precedence: cross-platform override →
  explicit version config → bundle Info.plist values → default
• Added comprehensive tests covering the new property and precedence rules
• Maintains full backward compatibility (optional parameter defaults to nil)

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)