Don't consider tasks for template unsafety if they're being skipped

[yajo]

          Consider migrations. Even if the template uses migrations, we only mark it as unsafe if the current update will trigger them.

In the same fashion, if it has tasks but you're ignoring them, there's no unsafety produced by tasks. Other unsafety criteria should still be honored, but not that one.

Originally posted by @yajo in #1561 (comment)

Actually we could even add ˋ--skip-tasksˋ as an alternative to ˋ--trustˋ when suggesting the user what to do with that unsafety.