#821 Upgrade to Eclipse 2024-09

• Best to review per commit.
• I followed our upgrade instructions. No changes needed for Java formatter, Java warnings/errors, etc. Two warnings for unnecessary casts fixed. Nothing surprising, I think.
• After merging this, all developers should upgrade their development environment, or set up a new one.
• This should fix #1016 (closed) for developers and end-users.

Closes #821 (closed)