Have separate types for every_is and is options

[alexander-yevsyukov]

This PR introduces a separate EveryIsOption type for the (every_is) file option. Previously the file option and the message option (is) were served by the same type called IsOption.

During the reimplementation of the code generation process in McJava it was decided that the generate flag of IsOption does not make sense for (is) option because it would produce a marker interface for only one message class.

So, this PR renames the existing IsOption into EveryIsOption and introduces new IsOption type which does not have the generate flag.

Other notable changes

• The constraint_for message option was deprecated because new Validation library does not support this mechanism which turned to be really hard to use.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.96%. Comparing base (de60491) to head (e0a58cf).
Report is 6 commits behind head on master.

Additional details and impacted files

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  Coverage     74.96%   74.96%           
  Complexity     1170     1170           
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  Files           189      189           
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  Branches        338      338           
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  Hits           3183     3183           
  Misses          932      932           
  Partials        131      131