[Enhancement]: converter改成extension机制

[yyuuttaaoo]

Concisely describe the proposed feature A clear and concise description of what you want. For example,

The log format collected to Kafka is not friendly to subsequent processing

Describe the solution you'd like (if any) A clear and concise description of what you want to achieve and implement. For example,

I would like to add an log flush method for flusher_kafka.

Additional comments Add any other context or screenshots about the feature request here. For example, the ideal input and output logs.

The logs are supposed to have the following contents, e.g.,

{"_target_":"127.0.0.1","_field_":"DISMAN-EXPRESSION-MIB::sysUpTimeInstance","_oid_":".1.3.6.1.2.1.1.3.0","_type_":"TimeTicks","_content_":"10423593"}