feat: add parameter to changelog generation

[dornech]

... to identify incremental generation run in the jinja template. This allows to include / exclude f. e. header lines form the current generation run to avoid multiple generation of header line(s)

Please refer to https://github.com/commitizen-tools/commitizen/discussions/1620

[bearomorphism]

It'd be better to add test cases related to #1620, thanks.

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 98.25%. Comparing base (120d514) to head (2facaca). :warning: Report is 807 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1625      +/-   ##
==========================================
+ Coverage   97.33%   98.25%   +0.91%     
==========================================
  Files          42       58      +16     
  Lines        2104     2694     +590     
==========================================
+ Hits         2048     2647     +599     
+ Misses         56       47       -9     

Flag	Coverage Δ
unittests	98.25% <ø> (+0.91%)	:arrow_up:

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