598 modify plugin trim filter

[HeadHunter483]

Description

Add trim filter to modify plugin. It has three modes: trim all, trim left and trim right. The filter accepts two arguments: mode and a cutset (substring to trim).

Fixes #598

[codecov]

Codecov Report

Attention: Patch coverage is 87.05882% with 33 lines in your changes are missing coverage. Please review.

Project coverage is 70.84%. Comparing base (8f3cbe4) to head (b93998b).
Report is 2 commits behind head on master.

❗ Current head b93998b differs from pull request most recent head be81b75. Consider uploading reports for the commit be81b75 to get more accurate results

Files	Patch %	Lines
cfg/substitution/regex_filter.go	78.35%	14 Missing and 7 partials ⚠️
cfg/substitution/trim_filter.go	86.36%	6 Missing and 3 partials ⚠️
cfg/substitution/filter.go	96.73%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #599      +/-   ##
==========================================
+ Coverage   70.64%   70.84%   +0.19%     
==========================================
  Files         119      122       +3     
  Lines       12340    12408      +68     
==========================================
+ Hits         8718     8790      +72     
+ Misses       3110     3108       -2     
+ Partials      512      510       -2     

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