Cleanup the compiler warnings that GitHub generates

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

Github is generating warnings for many things in the code base, even for files that do not change. Go over all of the warnings and clean up the code to remove these warnings. You can see the warnings in the PR link below.

https://github.com/microsoft/electionguard-cpp/pull/306/files

### Expected Behavior

Github will continue to add things that are problem, but we need to get code base to compile cleaner.

### Steps To Reproduce

_No response_

### Environment

```markdown
- OS:
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### Anything else?

_No response_

首先检查 pull request #306 中显示的编译器警告，然后编译仓库以确认当前的警告集合。清理整个代码库中报告的警告，并验证项目在移除这些警告后能够成功编译。

由索引模型根据 Issue 内容生成。