ci: add DynamicExpressions integration tests

[MilesCranmer]

DynamicExpressions.jl seems to be good at flagging issues in Enzyme, such as the below, so this PR therefore adds a simple integration test for it so that these issues will get flagged immediately.

• Task switch error when evaluating simple expression #548
• Recursive tree traversal-based expression evaluation produces no gradients #552
• Crash when trying to differentiate DynamicExpressions.jl #816
• Understanding Error: Enzyme aligned size and Julia size disagree #999
• Catching assertions / debugging mode? #1009
• Hanging and task switch errors when differentiating DynamicExpressions.jl #1018
• Extremely long compilation time on recursive, branching functions (DynamicExpressions.jl) #1156
• Hitting new segfaults in DynamicExpressions.jl #1662
• Missing 2-argument method for bitcast! #1674

The CI also pins DynamicExpressions to a specific version where it has been known to work, so any failures would indicate some kind of internal regression. Also, this is a separate CI run so won't be recorded in the main test suite.

This is also important for the stability of the PySR/SymbolicRegression.jl ecosystem which have a large number of non-technical users; I would want to prevent breakages for them when I eventually make Enzyme part of the default search code.

I restructured the CI so that packages can add their own integration tests fairly easily:

    matrix:
      version:
        - '1'
      os:
        - ubuntu-latest
      test:
        - DynamicExpressions
    steps:
      - uses: actions/checkout@v4
      - uses: julia-actions/setup-julia@v1
        with:
          version: ${{ matrix.version }}
      - uses: julia-actions/cache@v1
      - uses: julia-actions/julia-buildpkg@v1
      - name: "Run tests"
        run: |
            julia --color=yes --project=. -e 'using Pkg; pkg"instantiate"'
            julia --color=yes --project=test/integration -e 'using Pkg; pkg"dev ."; pkg"instantiate"'
            julia --color=yes --project=test/integration --threads=auto --check-bounds=yes -e test/integration/${{ matrix.test }}.jl
        shell: bash

All they need to do is create a new test/integration/{PackageName}.jl file and add it to the list.

@gdalle maybe you could rebase #1563 on this so we can have them in the same format?

[wsmoses]

SGTM!

[MilesCranmer]

Cool, seems to work!

(I think the #1674 is a different issue)

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.35%. Comparing base (5fc2309) to head (9fcbcae).

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #1675       +/-   ##
===========================================
+ Coverage   70.60%   96.35%   +25.74%     
===========================================
  Files          31        9       -22     
  Lines       12926      411    -12515     
===========================================
- Hits         9127      396     -8731     
+ Misses       3799       15     -3784     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.