feat: add csp-violation-event-plugin

[anthony-ism]

This change adds a new plugin, CspViolationPlugin that is responsible for attaching its custom eventHandler to the securitypolicyviolation event. https://developer.mozilla.org/en-US/docs/Web/API/Element/securitypolicyviolation_event

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[williazz]

Thanks for bringing attention to this new category of RUM events. This CR looks really good and I don't see any bugs at first glance.

However, I would like this plugin to be extensible for other security issues, and to use the best reporting tool available. From some quick research, I suspect that we should be monitoring security related issues using the ReportingObserver API. https://developer.mozilla.org/en-US/docs/Web/API/ReportingObserver

1. Could you refactor from EventListeners to ReportingObserver?
2. I suspect we should refactor this to a generic SecurityPlugin, but add a configuration option if rum users want to record CSP Violations (by default disabled). This way, we can easily extend your plugin to capture other security events as necessary.
3. Last, for knowledge share, please let me know what other security telemetries you are interested in recording, so I can try to get priority.

Thanks