Refactor HTMX Viewsets

[shapiromatron]

Refactor our lit.workflows and assessment.attachments HTMX ViewSets to use new .show-only-child class and remove nearly-identical templates between eco and epiv2 viewsets. This uses the pattern originally used in #989.

• show-only-child hides an element unless it is the only child of a parent element
• hide-empty-tbody will hide an element unless it has a child <tbody> containing a <tr> element
• Fix deletion script for eco class; cascading deletions are now properly displayed in the eco update page (i.e., deleting a Cause will immediately remove related Results from the table)

[caseyhans]

LGTM! @shapiromatron back to you

[shapiromatron]

Sorry it took me so long to review your changes @caseyhans, they all looked great, and I really like the generalized templates. This will make things simple, and it's really nice to have such a consistent pattern to use for future work.

I made a number of extremely minor changes, please merge if you're happy with the changes:

• c1fcfee add a few more newline characters (20 minutes ago)
• 4d0728d use helpers instead of manual html (52 minutes ago)
• b19d661 add trailing newline (69 minutes ago)
• e1dcb39 make script ID more specific (69 minutes ago)
• e00e06c rename class for clarity (70 minutes ago)
• ff8c1fe remove unused variable (70 minutes ago)

[caseyhans]

LGTM!