Add subject field to all *OptionDiscovered events

[yevhenii-nadtochii]

This PR adds subject field to all *OptionDiscovered events.

Having this field instead of just FieldName, TypeName and so on, helps to validate the option right in Policy upon the *OptionDiscovered event. Otherwise, we have to collect the required data in a view and only then validate. And the view doesn't know whether a member is marked with the option in advance.

Currently, we already have subject for FieldOptionDiscovered and OneofOptionDiscovered events. This change set suggests propagating this property to all similar events:

• TypeOptionDiscovered (replace type: TypeName → subject: MessageType)
• EnumOptionDiscovered (replace type: TypeName → subject: EnumType)
• EnumConstantOptionDiscovered (replace type: TypeName, constant: ConstantName → subject: EnumConstant)
• ServiceOptionDiscovered (replace service: ServiceName → subject: Service)
• RpcOptionDiscovered (replace service: ServiceName, rpc: RpcName → subject: Rpc)

The only exception is FileOptionDiscovered, which will continue to have just file: File for the following reasons:

1. The file: File property is requested by FileAware interface, which is implemented by everyast event.
2. Having a property with the same value under a different name subject: File has no sense.

Additionally, I suggest renaming of TypeOptionDiscovered to MessageOptionDiscovered. A type can be a message or enum, but we already have EnumOptionDiscovered event for that.

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 74.82%. Comparing base (a928b76) to head (2d6789e).
Report is 8 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #347      +/-   ##
============================================
+ Coverage     74.81%   74.82%   +0.01%     
  Complexity      615      615              
============================================
  Files           196      196              
  Lines          4256     4254       -2     
  Branches        396      396              
============================================
- Hits           3184     3183       -1     
+ Misses          939      938       -1     
  Partials        133      133              

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[yevhenii-nadtochii]

@armiol @alexander-yevsyukov PTAL

[alexander-yevsyukov]

LGTM