Experiment: Move natvis files from src/etc/natvis to debugger_visualizer attributes

[clarfonthey]

This is the "easy part" of a massive rabbit hole that I fell into trying to figure out how the current debug visualizers for hashmaps could potentially be moved into the hashbrown crate, while still being able to leverage them for libstd.

For natvis, it's pretty easy to separate out what belongs where, and we basically already do this. This just takes it a slight step further and attempts to move them into their relevant crates, and we'll see if it breaks everything in CI. For lack of a better place, this moves the "intrinsic" (should probably be renamed to "primitive") natvis file into the libcore crate, since no_core is unstable anyway.

The Python scripts are an absolute mess, and that's going to take some asking around. So, instead of stalling this part on that being done, I decided to just offer this PR and we'll see if it can work and hopefully make it easier for people to modify the debug visualizers in the standard library, at least for Windows.

---

Worth also mentioning right now that I don't have a copy of Windows proper to test this on, so, I'm mostly relying on CI/others to verify that this actually doesn't break anything.

[rustbot]

r? @clubby789

rustbot has assigned @clubby789.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

Why was this reviewer chosen?

The reviewer was selected based on:

• Owners of files modified in this PR: bootstrap
• bootstrap expanded to 6 candidates
• Random selection from Mark-Simulacrum, clubby789, jieyouxu

[rustbot]

Some changes occurred in src/tools/compiletest

cc @jieyouxu

[bjorn3]

Why is this necessary? Shouldn't changing them trigger a rebuild of the standard library already and in turn cause all test results to be invalidated?

[clarfonthey]

I'm actually not sure, but I wasn't even sure this would work at first, so, I was being cautious

[bjorn3]

rust/compiler/rustc_codegen_ssa/src/back/linker.rs

Lines 1087 to 1105 in a3903b1

	// This will cause the Microsoft linker to embed .natvis info into the PDB file
	let natvis_dir_path = self.sess.opts.sysroot.path().join("lib\\rustlib\\etc");
	if let Ok(natvis_dir) = fs::read_dir(&natvis_dir_path) {
	for entry in natvis_dir {
	match entry {
	Ok(entry) => {
	let path = entry.path();
	if path.extension() == Some("natvis".as_ref()) {
	let mut arg = OsString::from("/NATVIS:");
	arg.push(path);
	self.link_arg(arg);
	}
	}
	Err(error) => {
	self.sess.dcx().emit_warn(errors::NoNatvisDirectory { error });
	}
	}
	}
	}

can be removed after these changes, right?