Update LLM integration and add new agent tools and utilities

Refactored LLM handling to use updated langchaingo models and tools, replacing gollm dependencies. Introduced agent-related utilities, tools, and counters for better modular functionality. Added a parser for LLM model configuration and revamped the answering mechanism with enhanced support for tool-based interaction.

pkg/agent/answertool.go

@@ -0,0 +1,10 @@
+package agent
+
+var AnswerTool = FromFunction(
+	func(ctx *Context, args struct {
+		Answer string `description:"the answer to the question"`
+	}) (FuncResponse, error) {
+		return FuncResponse{Result: args.Answer}, nil
+	}).
+	WithName("answer").
+	WithDescription("Answer the question")