scripted-diff: replace non-standard fixed width integer types (u_int... -> uint...)

Summary:

-BEGIN VERIFY SCRIPT-
sed -i 's/u_int/uint/g' $(git grep -l u_int)
-END VERIFY SCRIPT-

Fixed width integer types prefixed with u_int are not part of C++ (see https://en.cppreference.com/w/cpp/types/integer), so it's better to avoid and replace them with their standard-conforming counterparts. (For those interested in history, according to one theory those u_int... types have been introduced by BSD: https://stackoverflow.com/a/5163960, http://lists.freedesktop.org/archives/release-wranglers/2004-August/000923.html).

This is a backport of core#25115

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D13243