Sniff idea: Detect when constant is being used in constant()

## Describe the solution you'd like

Not sure if VIPCS is the best way forward, but I think this would be a worthy sniff.

When using `constant()`, we should throw a warning if a string is not being inputted. Of course it is valid PHP to do something like:

```
constant( FOO_BAR );
```

But I think most likely, what the user wants to do is:

```
constant( 'FOO_BAR' );
```

## What code should be reported as a violation?

```
constant( FOO_BAR );
```

## What code should *not* be reported as a violation?

```
constant( 'FOO_BAR' );
constant( "FOO_BAR" );
constant( $foo_bar );
```

首先检查现有的 VIPCS-PHP_CodeSniffer sniff 约定，以及 constant() 调用的表示方式。确认会报告 constant(FOO_BAR)，而带引号的字符串和变量不会被报告，并使用相关的 sniff 测试套件验证其行为。

由索引模型根据 Issue 内容生成。