Workbench Form Validation UI Updates

[emilyanndavis]

Description

Fixes #912.

Specifically:

• Updates permission error messages to distinguish between a directory vs. a file and include verbose permission type (e.g., "You must have write access to this directory" instead of "You must have w access to this file")
• Removes input type (directory, raster, csv, etc.) from error message UI and adds it to the corresponding label instead, to ensure this helpful info persists in the UI regardless of interaction state
• Adds aria-describedby to input fields to associate them with their error messages (for screen reader support)
• Adds custom styling to <select> (dropdown) form fields—including green border when valid—for more consistency with appearance of other form fields
• Top-aligns labels to prevent vertical shift when an error message appears
• Aligns start of error message with the left edge of its form field (instead of with the info button)

Checklist

• Updated HISTORY.rst and link to any relevant issue (if these changes are user-facing)
• [n/a] Updated the user's guide (if needed)
• Tested the Workbench UI (if relevant)

Representative screenshots

[davemfish]

Thanks, @emilyanndavis , this is all very thorough and clear! These will be nice enhancements to the UI.