Warn when `Sentry.init()` options with semantic effect are passed as `undefined`

[lforst]

Description

As pre-work to #13262 where we want to change the behavior of Sentry.init() options being passed as undefined not having an effect, we want to first start warning people that this behavior will change soon.

I would probably do this even when debug: false. Remember that any console.log()s need to be wrapped in a console sandbox.

[github-actions]

A PR closing this issue has just been released 🚀

This issue was referenced by PR #14450, which was included in the 8.41.0 release.