add line before binding and it's related

[isadliliying]

第一次提交PR,有描述不清楚的地方还请见谅并沟通,thanks

两个主要改动:

1. 在Location基类中增加了filtered的标记,代表该Location被Matcher处理后,是否被LocationFilter过滤掉

2. 添加BeforeLine类型的Binding及相关的Matcher

为什么需要暴露是否被过滤掉的状态呢?

• 因为在使用行来进行增强(InterceptorProcessor#process)时发现如果没有明确出 匹配失败 和 被过滤 两种状态的话,在外层逻辑上没法做对应的处理(Arthas中无法判定是否需要注册listener)

为什么需要定义一个BeforeLine呢?用Line不行嘛?

• 场景: 期待在Arthas获取到本地变量,选择的实现方式是在某行之前进行插桩
• Binding时行号传递: Line使用了LineNumberNode中的行号,当我需要在 方法退出前 进行插入时,这边使用了-1来代表这个位置,所以Line无法给到-1这个值,在注册监听器时,这是个问题
• LocationFilter过滤问题: LineLocationMatcher目前是没有应用过滤的,也就是会导致重复增强
• 行号重复: 目前在增强kotlin类的时候发现,kotlin编译出来的class文件是存在重复行号问题的,使用LineLocationMatcher时候会尝试增强多个相同行号,LineBeforeLocationMatcher通过只取最前的一个来规避这个问题

thanks again

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