Startup --repair calls validate repair mode where documents that fail BSON validation are deleted. We need a jstest to check that --repair behaves correctly by deleting corrupt BSON records.

The existing code to delete corrupt BSON records during index rebuilds should be obsolete and can be deleted.

The existing code to delete corrupt BSON records during index rebuilds is still necessary for the case where collection files were salvaged and we rebuild indexes unconditionally.