fix(nextjs): Add default option to OnUncaughtException integration

[lforst]

As @lobsterkatie mentioned in #6138 (comment) we should properly address what happens if users modify the OnUncaughtException integration.

[lobsterkatie]

Thanks for running with my comment!

Two things I notice here:

• In the case in which a user either provides an integrations array which includes an instance of onUncaughtException or provides a function which returns such an array, this will work, because it will update that instance with the new option. In all other cases, however, the fact that there won't be an onUncaughtException instance in options.integrations when those options are passed to nodeInit means that the default instance (without the new option set) will end up being included. If we want the integration to exist with the new option, we have to add it at the addOrUpdateIntegration stage.

• I think we can do this a lot more simply, without having to duplicate most of the code in addOrUpdateIntegration.

I gave it a go in #6148.

[lobsterkatie]

Closed in favor of #6148.