Enable an extending entity to overwrite a requiredEntity binding

[ochnygosch]

Description

In case you extend an entity that has a requiredEntity and add a requiredEntity of the same type, then the requiredEntity of the
base entity is used.
This pull request changes this behaviour, so that the last requiredEntity of that specific type is used. This enables you to change
the content of a requiredEntity when extending an entity.

Sample

<entity name="BaseEntity" type="entity">
    <data key="test">Test</data>
    <requiredEntity type="subentity">BaseSubentity</requiredEntity>
</entity>
<entity name="BaseSubentity" type="subentity">
    <data key="subtest">BaseSubtest</data>
</entity>

<entity name="ExtEntity" type="entity" extends="BaseEntity">
    <requiredEntity type="subentity">ExtSubentity</requiredEntity>
</entity>
<entity name="ExtSubentity" type="subentity">
     <data key="subtest">ExtSubtest</data>
</entity>

Old Result for ExtEntity

{
  "entity" : {
    "test" : "Test",
    "sub" : {
       "subtest" : "BaseSubtest"
    }  
  }
}

New Result for ExtEntity

{
  "entity" : {
    "test" : "Test",
    "sub" : {
       "subtest" : "ExtSubtest"
    }  
  }
}

Fixed Issues (if relevant)

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/verification tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)
• Changes to Framework doesn't have backward incompatible changes for tests or have related Pull Request with fixes to tests

[jilu1]

@ochnygosch Thank you for your PR!
Mftf could not resolve entity reference with sample data provided above. Could you please check your sample data and add a verification test if possible before we further process this pr?

[jilu1]

https://jira.corp.magento.com/browse/MQE-2392

[jilu1]

@magento import pr to magento-commerce/magento2-functional-testing-framework

[magento-engcom-team]

@jilu1 the pull request successfully imported.