Add additional tests to the Java branch - #1131

• Add Example04CombineLLMPromptsAndNativeCodeTest
• Remove some left over code from previous attempts at immutability in skill/function collections
• Add annotations to allow use of dependency injection

Motivation and Context

Description

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows SK Contribution Guidelines (https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
• The code follows the .NET coding conventions (https://learn.microsoft.com/dotnet/csharp/fundamentals/coding-style/coding-conventions) verified with dotnet format
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄