MET-5092: Prepare publisher facing API for Unity plugin

[antonurankar-moloco]

Summary

Streamlines the Metica SDK initialization flow by separating core configuration from mediation setup, while adding GDPR/CCPA privacy controls for better compliance.

What's Changed

🔄 Initialization API Redesign

• Split monolithic MeticaConfiguration into focused MeticaInitConfig (core SDK params) and MeticaMediationInfo (ad network config)
• Replaced confusing MeticaAdsAssignmentStatus enum with clearer MeticaUserGroup model
• Changed return type from MeticaInitializationResult to MeticaInitResponse with direct SmartFloors access

🔒 Privacy Compliance

• Added SetHasUserConsent(bool) for GDPR consent management
• Added SetDoNotSell(bool) for CCPA compliance
• Both methods properly propagate to native Android/iOS layers

🧹 Code Quality

• Fixed inconsistent property casing (userGroup → UserGroup, isSuccess → IsSuccess)
• Removed unused/deprecated fields (Version, CustomKeys, configurable BaseEndpoint)
• Marked obsolete extension methods appropriately
• Hardcoded production endpoint to reduce configuration errors

Breaking Changes ⚠️

Before:

var config = new MeticaConfiguration {
    ApiKey = "your-api-key",
    AppId = "your-app-id", 
    UserId = "user-123",
    BaseEndpoint = "https://api.metica.com"
    Version = "1.15.5"
};
var result = await MeticaSdk.InitializeAsync(config);
if (result.IsMeticaAdsEnabled) { /* ... */ }

After:

var config = new MeticaInitConfig("your-api-key", "your-app-id", "user-123");
var mediation = new MeticaMediationInfo(
    MeticaMediationType.MAX,
    "your-applovin-sdk-key"
);
var response = await MeticaSdk.InitializeAsync(config, mediation);
if (response.SmartFloors.UserGroup == MeticaUserGroup.TRIAL) { /* ... */ }