Don't report exceptions from third-party code to Sentry

Created by: lguychard

We currently receive errors originating from third-party code in Sentry/browser-extension, for example:

• https://sentry.io/share/issue/b3241ea3ef1a4347a71e1f789b6c3732/
• https://sentry.io/share/issue/ce94f89bf900465ba2f0b1f5a1e65336/
• https://sentry.io/share/issue/2d47fbde245147c59760dcb53f644323/

This filters out such errors by checking the stack trace of exceptions in Sentry's beforeSend callback: strack traces where no filename contains our extension ID are discarded.