Add caching options for system messages and tools in Anthropic LLM

[leecjohnny]

TL;DR

Added caching support for system messages and tool definitions in the Anthropic LLM plugin.

What changed?

• Added cache_system and cache_tools boolean options to LLMOptions
• Implemented caching for system messages by adding cache control parameters when enabled
• Added cache control support for tool/function definitions
• Modified _latest_system_message and _build_function_description to handle caching configuration

How to test?

1. Initialize the Anthropic LLM with caching enabled:

llm = LLM(..., cache_system=True, cache_tools=True)

2. Run chat interactions with system messages and tool definitions
3. Verify that system messages and tools are properly cached in the Anthropic API responses

Why make this change?

Caching system messages and tool definitions can improve performance and reduce token usage by allowing the Anthropic API to optimize repeated content across requests. This is particularly beneficial in long-running conversations or when using the same tools across multiple interactions.

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[davidzhao]

thanks for the PR, there are a couple of tests that are failing, @leecjohnny could you take a look?

the ruff errors could be fixed with ruff format . && ruff check --fix .