refactor(BaseFormat): merge ChangelogFormat into BaseFormat

[bearomorphism]

Description

BaseFormat already looks like a base class for changelog format, but it has a parent class protocol ChangelogFormat. It is confusing to me.

Additionally, the protocol ChangelogFormat declares implementations of methods. I consider it confusing too.

This change addresses the unnecessary complexity and remove ChangelogFormat completely from the codebase. The alternative now is BaseFormat.

I am not sure if this is a breaking change. Please help to review.

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 98.29%. Comparing base (120d514) to head (03abf0d). :warning: Report is 842 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1612      +/-   ##
==========================================
+ Coverage   97.33%   98.29%   +0.95%     
==========================================
  Files          42       58      +16     
  Lines        2104     2695     +591     
==========================================
+ Hits         2048     2649     +601     
+ Misses         56       46      -10     

Flag	Coverage Δ
unittests	98.29% <100.00%> (+0.95%)	:arrow_up:

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[Lee-W]

I think @noirbizarre might be a better person to take a look at this one. My guts feeling tells me ChangelogFormat is mostly for typing