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};
 

crates/egui_inspection/src/protocol.rs

@@ -136,7 +136,7 @@ pub struct EncodedPng {
 /// Hard cap on a single framed message. Matches the sanity limit enforced by both ends.
 pub const MAX_MESSAGE_BYTES: usize = 256 * 1024 * 1024; // 256 MiB
 
-fn invalid_data(err: impl std::fmt::Display) -> io::Error {
+fn invalid_data(err: impl core::fmt::Display) -> io::Error {
     io::Error::new(io::ErrorKind::InvalidData, err.to_string())
 }