[v8] Remove `@sentry/tracing` package

[mydea]

Since quite a long time, there is no need anymore to install @sentry/tracing - anything that used to be there can & should be imported directly from your package, e.g. import { BrowserTracing } from '@sentry/react'.

We have already marked all the exports as deprecated, but I wonder if we should show a more "in your face" deprecation warning (e.g. console.warn) for this?