Replace StyleCI with PHP CS Fixer

[mspirkov]

Q	A
Is bugfix?	❌
New feature?	❌
Breaks BC?	❌
Fixed issues	comma-separated list of tickets # fixed by the PR, if any

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.33%. Comparing base (756c264) to head (67ef97d).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #137   +/-   ##
=========================================
  Coverage     99.33%   99.33%           
  Complexity      162      162           
=========================================
  Files            11       11           
  Lines           451      452    +1     
=========================================
+ Hits            448      449    +1     
  Misses            3        3           

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