fix(nextjs): Allow onUncaughtException integration to remain excluded

[lobsterkatie]

In the nextjs SDK, the addOrUpdateIntegration function exists to force the inclusion of certain integrations with certain options set. If such an integration is included in the underlying SDK's default integrations, however, (in other words, if it's included in the defaults set by @sentry/browser or @sentry/node), it's possible for the user to have actively chosen to exclude it, which we would then be overriding. This PR adds to the addOrUpdateIntegration logic to provide the ability to respect that choice.

The only way for a user to choose to filter out a default integration is by providing a function as their integrations option in Sentry.init(). Therefore, when handling the function case, we can check if a given integration is included in the return value, and if it's not, not add the default instance we otherwise would. This is controlled by a flag on that default instance named allowExclusionByUser. If it's set to true, we'll perform the check and respect the user's choice. If it's set to false or not set at all, we'll continue to behave as we have, forcing the inclusion of the given integration.

The inspiration for this change is our recent inclusion of the onUncaughtException integration in the nextjs defaults. This PR therefore also applies the above change to that default instance.

Finally, the test suite for addOrUpdateIntegration has been entirely reworked, to ensure that it covers all possible cases.

Supersedes #6142.

[github-actions]

size-limit report 📦

Path	Size
@sentry/browser - ES5 CDN Bundle (gzipped + minified)	19.49 KB (0%)
@sentry/browser - ES5 CDN Bundle (minified)	60.35 KB (0%)
@sentry/browser - ES6 CDN Bundle (gzipped + minified)	18.12 KB (0%)
@sentry/browser - ES6 CDN Bundle (minified)	53.67 KB (0%)
@sentry/browser - Webpack (gzipped + minified)	19.86 KB (0%)
@sentry/browser - Webpack (minified)	65.12 KB (0%)
@sentry/react - Webpack (gzipped + minified)	19.88 KB (0%)
@sentry/nextjs Client - Webpack (gzipped + minified)	45.81 KB (+0.06% 🔺)
@sentry/browser + @sentry/tracing - ES5 CDN Bundle (gzipped + minified)	26.24 KB (-0.01% 🔽)
@sentry/browser + @sentry/tracing - ES6 CDN Bundle (gzipped + minified)	24.62 KB (-0.01% 🔽)