Better handling of public pages and workflows authored by deleted users

[jdavcs]

Ref: #19343

to do:

• list of public pages: do not display pages authored by deleted users
• list of public workflows: do not display workflows authored by deleted users
• public page view: replace purged user hash with "archived user"; remove link
• public workflow view: same as above

(Please replace this header with a description of your pull request. Please include BOTH what you did and why you made the changes. The "why" may simply be citing a relevant Galaxy issue.)
(If fixing a bug, please add any relevant error or traceback)
(For UI components, it is recommended to include screenshots or screencasts)

How to test the changes?

(Select all options that apply)

• I've included appropriate automated tests.
• This is a refactoring of components with existing test coverage.
• Instructions for manual testing are as follows:
  1. Create 2 new users
  2. Login as each user and create a page and a workflow; publish page and workflow, share workflow with your main user
  3. Delete one of the users
  4. Login as main user
  5. View public pages; verify that pages by the deleted user are not displayed
  6. View public workflows; verify that workflows by the deleted user are not displayed.
  7. View shared workflows, verify same as above.

License

• I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.

[jdavcs]

@mvdbeek yes, owner_deleted_or_purged doesn't look right. There are only 19 not deleted but purged records on main, which I'll fix manually. Here, we can switch to checking deleted status only: owner_deleted - would that be a better approach?