Add CI validation of using common packages

### What is the problem or limitation you are having?

#1970 revealed that a very common package (setuptools) couldn't be packaged by Briefcase in a macOS.

### Describe the solution you'd like

We should perform validation that common/known problematic packages can be packaged as part of a Briefcase app.

This is *most* risky on macOS because of the binary merging process; but it would likely be worth validating on other platforms to make sure there are no quirks (e.g., on Flatpak).

### Describe alternatives you've considered

Do nothing; the status quo *works*, it's just not as proactive.

### Additional context

We made a similar change recently (#1910) to include `pyside-addons` in the automation tests to ensure that PySide apps can be signed on macOS; the underlying problem is very similar here.

Came up in the context of #1972, and validating that `setuptools` could be packaged.

Review the automation tests added in #1910 and the context around #1972 and #1970. Determine how a Briefcase app currently packages setuptools and how macOS binary merging and other platforms such as Flatpak are exercised. Done means CI validates packaging for common or known-problematic packages across the selected platforms.

Written by the indexing model from the issue text.