Prep for v1.12.0

[odow]

Pre-release

• Check that the pinned packages in docs/Project.toml are updated. We pin
  the versions so that changes in the solvers (changes in printing, small
  numeric changes) do not break the printing of the JuMP docs in arbitrary
  commits.
• Check that the rev fields in docs/packages.toml are updated. We pin
  the versions of solvers and extensions to ensure that changes to their
  READMEs do not break the JuMP docs in arbitrary commits, and to ensure
  that the versions are compatible with the latest JuMP and
  MathOptInterface releases.
• Update docs/src/changelog.md
• https://github.com/jump-dev/JuMP.jl/actions/runs/5217354658
• Change the version number in Project.toml
• Update the links in README.md
• The commit messages in this PR do not contain [ci skip]

The release

• After merging this pull request, comment @JuliaRegistrator register in
  the GitHub commit. This should automatically publish a new version to the
  Julia registry, as well as create a tag, and rebuild the documentation
  for this tag.

  These steps can take quite a bit of time (1 hour or more), so don't be
  surprised if the new documentation takes a while to appear. In addition,
  the links in the README will be broken until JuliaHub fetches the new
  version on their servers.
  

Post-release

• Once the tag is created, update the relevant release- branch. The latest
  release branch at the time of writing is release-1.0 (we haven't
  back-ported any patches that needed to create a release-1.Y branch). To
  to update the release branch with the v1.10.0 tag, do:
  git checkout release-1.0 git pull git merge v1.10.0 git push

[JuliaRegistrator]

Comments on pull requests will not trigger Registrator, as it is disabled. Please try commenting on a commit or issue.

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.08 ⚠️

Comparison is base (269742f) 98.05% compared to head (3db0067) 97.97%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3417      +/-   ##
==========================================
- Coverage   98.05%   97.97%   -0.08%     
==========================================
  Files          34       34              
  Lines        4924     4928       +4     
==========================================
  Hits         4828     4828              
- Misses         96      100       +4     

see 5 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
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[odow]

Bump @blegat. Lot's of stuff here.