Prep for v1.51.1

[odow]

Basic

• 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

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

Tests

• https://github.com/jump-dev/MathOptInterface.jl/actions/runs/26428199400
• If new tests were added, ensure that MOI.Test.version_added is implemented.

[blegat]

We should first tag v1.51.1 without #3001, so that people see with the new tests that they don't implement bridge cost correctly, and then we add #3001 in v1.52

[odow]

I regarded them both as a bug-fix. What's the problem with just making a single release? The only relevant failure is DiffOpt.

[blegat]

We might have failures in other packages that we don't test. Even if they are bug-fixes, that will break existing code.