More information for sampled Sentry transaction in breadcrumbs

In https://github.com/getsentry/sentry/pull/50425, transactions in breadcrumbs were changed to be shown as the transaction name if found (that is clickable) or just the ID if the transaction cannot be found.

Would be good to add in an info bubble or blurb about why that transaction cannot be found to make it more clear.

Start with pull request #50425, which changed how transactions appear in breadcrumbs, and trace the related breadcrumb UI. Determine why an unavailable transaction is shown only by ID and identify the appropriate place for explanatory text. Done means the UI explains why the transaction cannot be found while preserving the existing linked-name and ID behavior.

Written by the indexing model from the issue text.