fix: Remove system tests from generated packages

[danieljbruce]

Description

Solves issue #8021 by doing the following:

• Removes system tests that are not needed anymore
• Modifies package.json files so that they do not try to run the deleted system tests

Impact

• Improves CI runtime
• Removes generated tests which are guaranteed to pass and therefore don't provide any value.

[gemini-code-assist]

Code Review

This pull request removes the pack-n-play dependency and associated system tests across numerous Google Cloud client library packages, generally replacing the system-test script with a placeholder. The review identifies that the system-test script was not updated in the package.json files for google-cloud-automl, google-cloud-billing-budgets, and google-cloud-compute, which will likely cause execution failures. These scripts should be updated to "echo no system tests" for consistency and to prevent build errors.

[gemini-code-assist]

The pack-n-play dependency and its corresponding system tests have been removed, but the system-test script was not updated. This will likely cause npm run system-test to fail. Please update the script to "echo no system tests" for consistency with other packages in this PR.

[gemini-code-assist]

The pack-n-play dependency and its corresponding system tests have been removed, but the system-test script was not updated. This will likely cause npm run system-test to fail. Please update the script to "echo no system tests" for consistency with other packages in this PR.

[gemini-code-assist]

The pack-n-play dependency and its corresponding system tests have been removed, but the system-test script was not updated. This will likely cause npm run system-test to fail. Please update the script to "echo no system tests" for consistency with other packages in this PR.