Add per-workout flights climbed and swimming stroke count

[zkrige]

Summary

Exposes two per-workout HealthKit totals that were not previously surfaced by the plugin:

• Flights climbed (HKWorkout.totalFlightsClimbed)
• Swimming stroke count (HKWorkout.totalSwimmingStrokeCount)

Both are direct HKWorkout properties. The workout's duration (seconds) is also added to the emitted dictionary for completeness.

Changes

iOS (ios/Classes/HealthDataReader.swift) — both [HKWorkout] branches (the list read used by getHealthDataFromTypes and the single-sample read) now emit totalFlightsClimbed, totalSwimmingStrokeCount (in HKUnit.count(), null when the property is nil), and duration.

Dart (lib/src/health_value_types.dart) — WorkoutHealthValue gains nullable int? totalFlightsClimbed and int? totalSwimmingStrokeCount fields, parsed in fromHealthDataPoint mirroring totalSteps/totalDistance, and wired into the constructor, toString, ==, and hashCode.

Generated (lib/health.g.dart) — regenerated via dart run build_runner build to include the new fields in JSON (de)serialization.

These are additive and nullable, so existing consumers are unaffected. Values are null on Android (HealthKit-only properties).