fix(js-sdk): Move tracePropagationTargets to top level config

[AbhiPrasad]

In #51797 we bumped the JS SDK to 7.57.0. Changelog here: https://github.com/getsentry/sentry-javascript/releases/tag/7.57.0

Notable in this release was adding the ability to set tracePropagationTargets as a top level option to Sentry.init. Previously tracePropagationTargets was a nested option inside the BrowserTracing integration.

// old way
Sentry.init({
  integrations: [
   Sentry.BrowserTracing({
      tracePropagationTargets: ['foo', 'bar'],
    }),
  ],
});

// new with `7.57.0`
Sentry.init({
  integrations: [new Sentry.BrowserTracing()],
  // controls what requests trace headers attached - required because cors 😭
  tracePropagationTargets: ['foo', 'bar']
});

This change is done in a backwards compat manner though, so that if you defined tracePropagationTargets in BrowserTracing, it is considered valid. What's notable is that we made the decision to say that defining a top level tracePropagationTargets (in Sentry.init) would override the tracePropagationTargets set in BrowserTracing options - this minimized the bundle size of the backwards compat change.

Unfortunately, our sdk init code in the sentry frontend was unintentionally setting tracePropagationTargets in the top level, via the spread operator.

sentryConfig as {
  allowUrls: string[];
  dsn: string;
  release: string;
  tracePropagationTargets: string[];
  profilesSampleRate?: number;
};

Sentry.init({
    // This defines tracePropagationTargets on the init options object
    ...sentryConfig,
// ...

Previously this did nothing, but with the bump to 7.57.0, we started to use this top level tracePropagationTargets instead of the one in BrowserTracing. This means we removed the /^\// target in ['localhost', /^\//, ...extraTracePropagationTargets], which meant we stopped attaching headers to our outgoing api requests.

This PR fixes this predicament by removing the usage of BrowserTracing tracePropagationTargets in favour of using the top level option.

[AbhiPrasad]

Validated this in dev-ui and running sentry locally, but would appreciate if someone also pulled and tested to double check.