fix(test): Upgrade integration test to webpack 4

[lobsterkatie]

This upgrades the integration test to use webpack 4, as continuing to use webpack 3 (which hasn't been current for almost 6 years) was spamming the console with specious errors. It also upgrades other dependencies as needed to work with webpack 4. Finally, it makes a few adjustments to our test commands, so that they'll work in both Node 8 and 18. (Out of the box, Webpack 4 wants a node version higher than 8 but lower than 18, but we can get around this by using a combination of --ignore-engines when installing and --openssl-legacy-provider when running the tests.)

[codecov-commenter]

Codecov Report

Base: 0.00% // Head: 0.00% // No change to project coverage :thumbsup:

Coverage data is based on head (1abb375) compared to base (e04db0a). Patch has no changes to coverable lines.

:exclamation: Current head 1abb375 differs from pull request most recent head 3a14915. Consider uploading reports for the commit 3a14915 to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #400 +/- ## ============================= ============================= ``` Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=getsentry). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=getsentry)

:umbrella: View full report at Codecov.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.

[lforst]

Closing because we moved the plugin to https://github.com/getsentry/sentry-javascript-bundler-plugins (where we test with webpack 4 :D)