Clean up HMIS Data Source factories, clarify usage

[gigxz]

Merging this PR

• use the squash-merge strategy for PRs targeting a release-X branch
• use a merge-commit or rebase strategy for PRs targeting the stable branch

Description

• Give NON-primary data source fixture unique name/short_names to reduce confusion in debugging
• Update HMIS ds to always be authoritative and user the same source_type we us in prod
• Update hmis json form seed helper to (1) add comment clarifying how to use with hmis base setup, and (2) find_by hostname only

Type of change

Test cleanup

Checklist before requesting review

• I have performed a self-review of my code
• I have run the code that is being changed under ideal conditions, and it doesn't fail
• If adding a new endpoint / exposing data in a new way, I have:
  • ensured the API can't leak data from other data sources
  • ensured this does not introduce N+1s
  • ensured permissions and visibility checks are performed in the right places
• Any major architectural changes are supported by an approved ADR (Architectural Decision Record)
• I have updated the documentation (or not applicable)
• I have added spec tests (or not applicable)
• I have provided testing instructions in this PR or the related issue (or not applicable)

[//]: # NOTE: system tests may fail if there is no branch on the hmis-frontend that matches the Source or Target branch of this PR. This is expected