Recreate legacy behaviour with just data collection if possible

[linear-code]

In the best case, we can create a data collection setting equivalent to sendDefaultPii for either true or false.

Worst case, we have to check if sendDefaultPii was set explicitly and then retain the legacy behaviour.

[linear-code]

PHP-87

[sentry-pierre]

Fixed the typo (retrain → retain) and tightened the wording so the two approaches read clearly. No material changes.