[Fix 376] Fix redunctantAllowNil false positive offense

[ngouy]

Fix 367

The issue occurs because we are checking the presence of allow_nil and allow_blank within the whole node tree
What we need to do is to check only the presence of this both when they are used on the same helper / level

If you want a specific message depending on the helper, it makes sense to have one or the other in different helpers of the same validation (CF issue)

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[koic]

Thanks!