Enable the clippy::std_instead_of_core lint (#8394)

Prefer `core::` over `std::` where either work

* Part of https://github.com/emilk/egui/issues/5735

crates/egui_inspection/src/plugin.rs

@@ -33,8 +33,8 @@
 //! Note that [`serve`]'s threads hold an [`egui::Context`] clone, so the context stays alive
 //! for as long as the listener runs (the lifetime of the process, for a debug attach).
 
+use core::time::Duration;
 use std::sync::mpsc;
-use std::time::Duration;
 
 use egui::{Context, FullOutput, RawInput};