use templated expr

[mccalluc]

• Towards Merge make_accuracy_histogram into shared.py #219

The root problem is that details are duplicated between the templates and db_helper.py. The original thought was that db_helper code could be moved into shared, but that by itself wouldn't fix the problem: the templates are still necessary. Putting everything in shared would result in less readable, less idiomatic generated code.

The course proposed here is to exec the templated code, and in some sense there is less duplication now... but just looking at the diff, it's hard to argue that this is actually simpler.

For the reviewer: Is it better to stick with the status quo, and tolerate some duplication of code, and close this PR without merging, and close the linked issue... or add complexity with exec, but have the polars expression in only one place? I'm on the fence.

[mccalluc]

CI failure. Re-running:

Run actions/upload-artifact@v4
  with:
    name: playwright-traces
    path: test-results/
    if-no-files-found: warn
    compression-level: 6
    overwrite: false
    include-hidden-files: false
  env:
    pythonLocation: /opt/hostedtoolcache/Python/3.13.3/x64
    PKG_CONFIG_PATH: /opt/hostedtoolcache/Python/3.13.3/x64/lib/pkgconfig
    Python_ROOT_DIR: /opt/hostedtoolcache/Python/3.13.3/x64
    Python2_ROOT_DIR: /opt/hostedtoolcache/Python/3.13.3/x64
    Python3_ROOT_DIR: /opt/hostedtoolcache/Python/3.13.3/x64
    LD_LIBRARY_PATH: /opt/hostedtoolcache/Python/3.13.3/x64/lib
With the provided path, there will be 1 file uploaded
Artifact name is valid!
Root directory input is valid!
Error: Failed to CreateArtifact: Received non-retryable error: Failed request: (409) Conflict: an artifact with this name already exists on the workflow run