Refactor ProcessorSplitRegexNative to ProcessorMergeMultilineLogNative and Introduce ProcessorSplitNative for Line-based Event Splitting

[quzard]

重构ProcessorSplitRegexNative插件为ProcessorMergeMultilineLogNative，原有的ProcessorSplitRegexNative是在同个content里进行多行切分。现在添加一个新的插件ProcessorSplitNative，用于将多行日志按照\n切分成多个event，然后再通过ProcessorMergeMultilineLogNative，按照多行正则配置，对event进行多行聚合。

此外ProcessorMergeMultilineLogNative插件增加一种行为——ProcessEventsWithPartLog。根据event里是否有PartLogFlag，来决定是否要合并event。例如如下：

{
    "events": [
        {
            "contents": {
                "PartLogFlag": "true",
                "content": "Exception"
            },
            "timestamp": 12345678901,
            "timestampNanosecond": 0,
            "type": 1
        },
        {
            "contents": {
                "PartLogFlag": "true",
                "content": " in thread"
            },
            "timestamp": 12345678902,
            "timestampNanosecond": 0,
            "type": 1
        },
        {
            "contents": {
                "PartLogFlag": "true",
                "content": "  'main'"
            },
            "timestamp": 12345678903,
            "timestampNanosecond": 0,
            "type": 1
        },
        {
            "contents": {
                "content": " java.lang.NullPoinntterException"
            },
            "timestamp": 12345678904,
            "timestampNanosecond": 0,
            "type": 1
        }
    ]
}

合并为：

{
    "events": [
        {
            "contents": {
                "content": "Exception in thread  'main' java.lang.NullPoinntterException"
            },
            "timestamp": 12345678901,
            "timestampNanosecond": 0,
            "type": 1
        }
    ]
}