fix(conf): Memory leak on loading YAML with cyclic dependencies

[DengY11]

I fixes a memory leak issue that occurred when loading a YAML configuration file with self-referencing structs. The previous implementation entered an infinite loop during type analysis, causing a stack overflow.
eg:

type Node struct {
    Name     string  `json:"name"`
    Children []*Node `json:"children,optional"`
}

Solution:
The fix introduces a robust cycle detection mechanism within the buildFieldsInfo function. It now uses a visited map to keep track of processed types.

I also add a test to show whether it works

close #5140

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[Copilot]

Pull Request Overview

Fixes a memory leak and stack overflow issue when loading YAML configurations with cyclic struct references. The problem occurred when structs contained self-referencing fields (like a Node with Children of type []*Node), causing infinite recursion during type analysis.

• Introduces cycle detection mechanism using a visited map to track processed types
• Refactors buildFieldsInfo function to accept and utilize the visited map parameter
• Consolidates buildStructFieldsInfo functionality directly into buildFieldsInfo

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
core/conf/config.go	Implements cycle detection by adding visited map parameter to buildFieldsInfo and related functions, removes buildStructFieldsInfo
core/conf/config_test.go	Updates test call to include new visited map parameter and adds comprehensive test for cyclic reference handling