chore: add resource loader for user agent generation

[mrehan27]

part of MBL-540

Changes

• Added SdkResourceLoader class to load resources from bundled SDK and generate SdkClient based on it
• Added tests for SdkResourceLoader

User Agents Generated:

Native iOS (Main Target):

Customer.io iOS Client/3.4.1 (arm64; iOS 18.0) io.customer.ios-sample.apn-spm.APN-UIKit/1.0

Native iOS (NSE):

Customer.io iOS Client/3.4.1 (arm64; iOS 18.0) io.customer.ios-sample.apn-spm.APN-UIKit.richpush/1.0

React Native iOS (Main Target):

Customer.io ReactNative Client/3.9.0 (arm64; iOS 18.0) io.customer.ami/1.0

React Native iOS (NSE):

Customer.io ReactNative Client/3.9.0 (arm64; iOS 18.0) io.customer.ami.richpush/1.0