Port parser filter of fluent-plugin-parser into core plugins.

[repeatedly]

Plugin repository is here: https://github.com/tagomoris/fluent-plugin-parser

parser filter is for parsing a field of record and update the record by using parsed result.
This is useful when forwarding device can't generate proper structured record, e.g. docker logging driver, embedded device, etc.
fluentd and docker combination is now widely used and lots of users use parser filter on production.

Porting parser filter has several merits.

• Reduce installation step in many cases
• Avoid parser filter breakage by fluentd version update
• Use parser filter to check updating parsers doesn't break existing API.

So time to port parser filter.