[BD] [BB-2503] Add Username column into ORA data report

Description

This PR adds `Username` field to the `ORA` data report. Currently, report contains only `Anonymized Student ID`.

[Report example before this change.](https://github.com/edx/edx-platform/files/4722869/TEST3_TEST3_TEST3_ORA_data_2020-06-03-0640.csv.tar.gz)

[Report example after this change.](https://github.com/edx/edx-platform/files/4722866/TEST3_TEST3_TEST3_ORA_data_2020-06-03-0811.csv.tar.gz)

*JIRA tickets*:

*Discussions*: None

*Dependencies*: None

*Merge deadline*: None

*Sandbox URL*: TBD - sandbox is being provisioned.

*Testing instructions*:

1. Checkout your `edx-platform` to this branch.
2. Restart `lms` service, if it didn't restart automatically.
3. Create course with `ORA` block or add it to any existing course.
4. Respond to questions in this block with a few users.
5. As a course staff, go to `<Your course>` -> `Instructor` -> `Data Download` (it's a tab in `Instructor Dashboard`) -> click `Generate ORA Data Report` button.
6. If you're testing this using docker devstack, you're unable to download report from the interface. You can find it inside container, in `/tmp/edx-s3/grades/` directory.
7. In downloaded report, you should see new column, `Username`.

*Author notes and concerns*:

1. I still wait for Marco's answer in ticket comments. Final report form depends on his answer.
2. I don't know if this comment useful:
```

  1. We perform this step here because don't want to modify ORA runtime
    ```
    Initially it was a little confusing for me why didn't we decide to change `edx-submissions` API response. Probably, it should be obvious for experienced developer.
    3. `TestInstructorOra2Report` needs some changes, and probably `ora2_data_with_deanonymized_usernames` also should be covered.

*Reviewers*

  • [ ] @giovannicimolin

  • [ ] edX reviewer[s] TBD

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Reporter

Open Source Pull Request Bot

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Contributor Name

Demid Avramenko

Repo

edx/edx-platform

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