Bugfix LH Veteran-Uploaded evidence filenames

[NB28VT]

This bug was caught through manual testing on staging. The error message returned "no filename" for this line

upload_document = provider.generate_upload_document(attachment.converted_filename)

It should fall back to the upload data "name" key as is done here with the existing: https://github.com/department-of-veterans-affairs/vets-api/blob/master/app/sidekiq/evss/disability_compensation_form/submit_uploads.rb#L162

Summary

• This work is behind a feature toggle (flipper): YES/NO
  YES - all LH migration code is behind flippers. The Veteran Upload job is being tested on staging before we roll it out to 1% of users.
• (Summarize the changes that have been made to the platform)
• (If bug, how to reproduce)
  On staging, perform the job again watch for error/success in datadog
• (What is the solution, why is this the solution?)
• (Which team do you work for, does your team own the maintenance of this component?)
  DBEX Team 2 Carbs
• (If introducing a flipper, what is the success criteria being targeted?)

Related issue(s)

• Link to ticket created in va.gov-team repo OR screenshot of Jira ticket if your team uses Jira
  [LH Doc Upload] Veteran-uploaded docs (bugfix) filename error va.gov-team#97277
• Link to previous change of the code/bug (if applicable)
• Link to epic if not included in ticket

Testing done

• New code is covered by unit tests
• Describe what the old behavior was prior to the change
• Describe the steps required to verify your changes are working as expected. Exclusively stating 'Specs run' is NOT acceptable as appropriate testing
• If this work is behind a flipper:
  • Tests need to be written for both the flipper on and flipper off scenarios. Docs.
  • What is the testing plan for rolling out the feature?

Screenshots

Note: Optional

What areas of the site does it impact?

(Describe what parts of the site are impacted andifcode touched other areas)

Acceptance criteria

• I fixed|updated|added unit tests and integration tests for each feature (if applicable).
• No error nor warning in the console.
• Events are being sent to the appropriate logging solution
• Documentation has been updated (link to documentation) N/A
• No sensitive information (i.e. PII/credentials/internal URLs/etc.) is captured in logging, hardcoded, or specs
• Feature/bug has a monitor built into Datadog (if applicable) The dashboard is being built / tested
• If app impacted requires authentication, did you login to a local build and verify all authenticated routes work as expected
• I added a screenshot of the developed feature

Requested Feedback

(OPTIONAL)What should the reviewers know in addition to the above. Is there anything specific you wish the reviewer to assist with. Do you have any concerns with this PR, why?

[freeheeling]

LGTM