GH-5293 Add Skill extension support for Spring AI

[zhanglinpeng-semir]

Introduce a comprehensive skill extension that enables dynamic skill loading, activation, and progressive skill integration with LLM conversations.

Key Features:

• Progressive loading: LLM can discover and load skills on-demand
• Multi-tenant support: Isolated skill activation per conversation
• Flexible registration: Support class-based and instance-based skills, easily extensible for more types
• Customizable skill capabilities: Support flexible extension and customization of diverse skill functionalities

Components:

• Core:
  • SkillKit: Central coordination of skill lifecycle management
  • SkillBox: Skill metadata storage and activation state tracking
  • SkillPoolManager: Lazy/eager skill instance loading and caching
  • SkillRegistrar: Interface class providing diversified skill registration capabilities
• SPI:
  • SkillAwareAdvisor: Responsible for loading skills into LLM prompts and managing conversation-level skill activation/deactivation
  • SkillAwareToolCallingManager: Manages automatic injection and execution of skill-associated tools; delegates execution and parsing of non-skill tools to other components
  • SkillAwareToolCallbackResolver: Works with SkillAwareToolCallingManager to enable dynamic tool execution by resolving tool callbacks from SkillBox's active skills
• Annotations:
  • Skill, SkillInit, SkillExtension, SkillContent, SkillTools, SkillReferences
• Tools:
  • Progressive skill loader tools for LLM interaction

== Semir Group Contribution ==
Developed by Semir Lab Team
Part of Semir's open source technology initiative
Original implementation: https://github.com/semir-lab/spring-ai-skill-extension

Fixes: #5293

Thank you for taking time to contribute this pull request!
Signed-off-by: LinPeng Zhang zhanglinpeng@semir.com

[zhanglinpeng-semir]

Here is a runnable example : spring-projects/spring-ai-examples#92