Refactor advisor architecture in Spring AI

This commit introduces a major overhaul of the advisor system in Spring AI,
improving modularity, type safety, and consistency

Core Changes:
- Replace RequestAdvisor and ResponseAdvisor with CallAroundAdvisor and StreamAroundAdvisor
- Introduce AdvisedRequest and AdvisedResponse classes for better encapsulation
- Deprecate RequestResponseAdvisor in favor of new advisor types
- Remove AdvisorObservableHelper class

Advisor Implementation Updates:
- Update AbstractChatMemoryAdvisor, MessageChatMemoryAdvisor, PromptChatMemoryAdvisor,
QuestionAnswerAdvisor, SafeGuardAroundAdvisor, SimpleLoggerAdvisor, and
VectorStoreChatMemoryAdvisor to implement new advisor interfaces
- Remove CacheAroundAdvisor (functionality likely moved elsewhere)
- Make CallAroundAdvisor and StreamAroundAdvisor extend Ordered interface

Client and Chain Management:
- Modify DefaultChatClient to use new advisor chain approach
- Refactor DefaultAroundAdvisorChain for better ordering and observation
- Implement builder pattern for advisor chain construction in DefaultChatClient
- Separate call and stream advisors in DefaultAroundAdvisorChain

Observation and Context Handling:
- Update observation conventions and context handling in advisors
- Add order field to AdvisorObservationContext
- Modify DefaultAdvisorObservationConvention to include order in high cardinality key values

Testing and Integration:
- Refactor ChatClientAdvisorTests and add new AdvisorsTests
- Update integration tests to reflect new advisor structure
- Enhance AdvisorsTests to verify correct advisor execution order

New Features:
- Generalize the Protect From Blocking functionality across all advisors
- Add (experimental) Re2 advisor to enhance reasoning capabilities of LLMs
- Add disabled Re2 test in OpenAiChatClientIT

Documentation:
- Add Advisors documentation
- Enhance advisors documentation with order explanation and Re2 example

Advisor Ordering:
- Introduce Advisor constants for precedence ordering
- Update AbstractChatMemoryAdvisor to use new precedence constant
- Improve advisor ordering and management in DefaultAroundAdvisorChain.Builder
- Remove redundant reordering logic from DefaultAroundAdvisorChain

These changes aim to provide a more flexible and powerful advisor system,
allowing for easier implementation of complex AI-driven interactions

Co-authored-by: Dariusz Jędrzejczyk <dariusz.jedrzejczyk@broadcom.com>

vector-stores/spring-ai-pgvector-store/src/test/java/org/springframework/ai/vectorstore/PgVectorStoreWithChatMemoryAdvisorIT.java

@@ -16,15 +16,21 @@
 
 package org.springframework.ai.vectorstore;
 
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import java.util.List;
+import java.util.Map;
+
 import org.jetbrains.annotations.NotNull;
-import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
 import org.mockito.ArgumentCaptor;
 import org.mockito.ArgumentMatchers;
 import org.mockito.Mockito;
-import org.mockito.invocation.InvocationOnMock;
-import org.mockito.stubbing.Answer;
 import org.postgresql.ds.PGSimpleDataSource;
 import org.springframework.ai.chat.client.ChatClient;
 import org.springframework.ai.chat.client.advisor.VectorStoreChatMemoryAdvisor;
@@ -41,12 +47,6 @@ import org.testcontainers.containers.PostgreSQLContainer;
 import org.testcontainers.junit.jupiter.Container;
 import org.testcontainers.junit.jupiter.Testcontainers;
 
-import java.util.List;
-import java.util.Map;
-
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.mockito.Mockito.*;
-
 /**
  * @author Fabian Krüger
  * @author Soby Chacko