[1.6.x] Revert "Fixed #20296 -- Allowed SafeData and EscapeData to be lazy"

This reverts commit 2ee447fb.

That commit introduced a regression (#21882) and didn't really
do what it was supposed to: while it did delay the evaluation
of lazy objects passed to mark_safe(), they weren't actually
marked as such so they could end up being escaped twice.

Refs #21882.

Backport of a878bf9b from master.