[ci] Fix test driver name

[ditman]

According to the docs, the test driver file must be called: test_driver/integration_test.dart.

This commit fixes the web plugins that don't follow the convention for their tests.

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the Flutter Style Guide and the C++, Objective-C, Java style guides.
• I signed the CLA.
• The title of the PR starts with the name of the plugin surrounded by square brackets, e.g. [shared_preferences]
• I listed at least one issue that this PR fixes in the description above.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy.
• I updated CHANGELOG.md to add a description of the change.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making or feature I am adding, or Hixie said the PR is test exempt.
• All existing and new tests are passing.

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[stuartmorgan-g]

LGTM. You should wait for #3738 to land and then rebase before landing this, since otherwise we'll be enabling tests on post-submit that have never run in presubmit.

[ditman]

Rebasing with #3738 now

[ditman]

PTAL @stuartmorgan, I had to do a small tweak to the run script for web tests that require an API key :/

[stuartmorgan-g]

LGTM modulo comment.