Add metric k8s multiline

[kirillov6]

Fixes #527

[codecov]

Codecov Report

Attention: 58 lines in your changes are missing coverage. Please review.

Comparison is base (beb2d16) 67.86% compared to head (9345603) 69.63%.
Report is 4 commits behind head on master.

Files	Patch %	Lines
plugin/action/split/split.go	55.26%	12 Missing and 5 partials ⚠️
pipeline/processor.go	73.80%	10 Missing and 1 partial ⚠️
pipeline/do_if.go	96.83%	7 Missing and 2 partials ⚠️
pipeline/event.go	69.23%	4 Missing ⚠️
fd/file.d.go	40.00%	2 Missing and 1 partial ⚠️
plugin/action/move/move.go	95.16%	2 Missing and 1 partial ⚠️
plugin/input/k8s/multiline_action.go	72.72%	2 Missing and 1 partial ⚠️
plugin/output/gelf/gelf.go	0.00%	3 Missing ⚠️
e2e/split_join/split_join.go	97.36%	2 Missing ⚠️
plugin/output/elasticsearch/elasticsearch.go	0.00%	2 Missing ⚠️
... and 1 more

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #528      +/-   ##
==========================================
+ Coverage   67.86%   69.63%   +1.76%     
==========================================
  Files         104      109       +5     
  Lines       10705    11327     +622     
==========================================
+ Hits         7265     7887     +622     
+ Misses       2977     2964      -13     
- Partials      463      476      +13     

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