Prep for v1.28.0

[odow]

TODO

• [x] #2451
• [x] #2470
• [x] #2472
• [x] #2473
• [x] #2474
• [x] #2475
• [x] #2476
• [x] #2477

Basic

• [x] version field of Project.toml has been updated
  • If a breaking change, increment the MAJOR field and reset others to 0
  • If adding new features, increment the MINOR field and reset PATCH to 0
  • If adding bug fixes or documentation changes, increment the PATCH field

Documentation

• [x] Add a new entry to docs/src/changelog.md, following existing style

Tests

• [x] https://github.com/jump-dev/MathOptInterface.jl/actions/runs/8607293206