Add `core::mem::DropGuard`

Fix CI for drop_guard

fix CI

fix all tidy lints

fix tidy link

add first batch of feedback from review

Add second batch of feedback from review

add third batch of feedback from review

fix failing test

Update library/core/src/mem/drop_guard.rs

Co-authored-by: Ruby Lazuli <general@patchmixolydic.com>

fix doctests

Implement changes from T-Libs-API review

And start tracking based on the tracking issue.

fix tidy lint