Adds try_find to Iterator.

PR: #63177

fn try_find<F, E, R>(&mut self, f: F) -> Result<Option<Self::Item>, E>
where
    F: FnMut(&Self::Item) -> R,
    R: Try<Ok = bool, Error = E>;

Open questions:

• Decide on just-Result, vs potentially supporting Option and other Try types Decide on generic-ness of functions like Iterator::try_find and array::try_map #85115
• Final commenting period (FCP)
• Stabilization PR