refactor: Simplifies VectorStoreChatMemoryAdvisor code

[cueon]

• The update refactors the VectorStoreChatMemoryAdvisor class by simplifying import statements, streamlining code for readability, and using more concise Java constructs. There are no changes to public APIs or core logic. All modifications focus on internal clarity, direct imports, and more idiomatic Java syntax.

• Readability: The code is refactored to improve readability by using local variables to hold intermediate results.

• Maintainability: The refactoring aims to enhance maintainability through clearer type declarations and a more structured approach.

• Code Style: The changes include using more explicit type declarations instead of var.

• All tests passed.

[ilayaperumalg]

@digitpic Thanks for the PR cleaning up/polishing the code.

[Amine-Kadi]

* Code Style: The changes include using more explicit type declarations instead of var.

Is there a style guide that forbid the usage of var ? The usage of var with the builder seems pretty fine and easy to read.

[cueon]

@Amine-Kadi
Thank you for replying.

I agree that using var in builder patterns can improve readability.
However, I decided to make the change because I believe that explicit type declarations are more beneficial for long-term code maintainability.

While using var does not clearly violate any style guide, explicitly declaring the type helps convey the intent of the code more clearly. Additionally, var can sometimes infer unintended types, which could lead to debugging overhead.

For these reasons, I consider explicit type declarations to be a safer and more consistent choice.

[markpollack]

fwiw, i tend to prefer explicit types in framework like code.

[ilayaperumalg]

@digitpic Thanks for the PR cleaning up the code. Rebased and merged as 3fee79a