Rollup merge of #64885 - andjo403:iter, r=scottmcm
Rollup merge of #64885 - andjo403:iter, r=scottmcm

use try_fold instead of try_for_each to reduce compile time

as it was stated in #64572 that the biggest gain was due to less code was generated I tried to reduce the number of functions to inline by using try_fold direct instead of calling try_for_each that calls try_fold.

as there is some gains with using the try_fold function this is maybe a way forward.
when I tried to compile the clap-rs benchmark I get times gains only some % from #64572

there is more function that use eg. fold that calls try_fold that also can be changed but the question is how mush "duplication" that is tolerated in std to give faster compile times

can someone start a perf run?

cc @nnethercote @scottmcm @bluss
r? @ghost

aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust