Handle the case where the Google Tag event settings are out of sync with the web data stream settings.

## Feature Description

As spotted by @wpdarren, and as mentioned [here](https://support.google.com/analytics/answer/9216061?hl=en), when using a Google Tag in conjunction with a data stream with enhanced measurement enabled, it's necessary to ensure that the relevant events are enabled in the Google Tag's config as well.

These can be configured in the Tag Manager UI (see screenshot below), or via the [API](https://developers.google.com/tag-platform/tag-manager/api/v2/reference/accounts/containers/workspaces/gtag_config). By default, all event types are enabled, so the scenario where there's a mismatch between the events settings will be another edge case that we need to consider.

Perhaps another warning notice would suffice for an MVP, and we could follow up with the ability to allow the user to sync the settings.


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## Acceptance criteria

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## Implementation Brief

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### Test Coverage

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## QA Brief

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## Changelog entry

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Start by tracing how Google Tag event settings and web data stream enhanced-measurement settings are represented and compared in the existing settings flow. Review the linked Google documentation and determine the MVP warning behavior before identifying the relevant UI and API entry points. Done means an out-of-sync configuration is detected and clearly surfaced to the user.

Written by the indexing model from the issue text.