Auto merge of #106458 - albertlarsan68:move-tests, r=jyn514

Move src/test to the root

See MCP at rust-lang/compiler-team#573

There may be more changes needed.

The first commit is just the move of the files:
You can check that the first commit did not do anything else than renames by running
```
git diff --diff-filter=r -M100% <rust-lang remote>/master <first commit hash>
```
The output should be empty, because the filter excludes renames, and the match threshold for qualifying a rename is 100%.

The second one is mostly a "find and replace" of `src/test` to `tests` and whatever is needed to make CI pass.

What is left to do:
---

- [x] Move directory
- [ ] Change references to `src/test`
    - [x] Change references in-tree
    - [ ] Change references in submodules / out-of-tree docs
- [x] Make CI pass:
    - [x] Fix tidy
    - [x] Fix tests
    - [x] Bless tests if needed (shouldn't normally)
- [ ] Merge it !

crates/hir-def/src/macro_expansion_tests/mbe/meta_syntax.rs

@@ -94,7 +94,7 @@ macro_rules! m2 { () => ( ${invalid()} ) }
 
 #[test]
 fn test_rustc_issue_57597() {
-    // <https://github.com/rust-lang/rust/blob/master/src/test/ui/issues/issue-57597.rs>
+    // <https://github.com/rust-lang/rust/blob/master/tests/ui/issues/issue-57597.rs>
     check(
         r#"
 macro_rules! m0 { ($($($i:ident)?)+) => {}; }

crates/ide-db/src/generated/lints.rs

@@ -3624,7 +3624,7 @@ of a library.
 Plugins can extend [Rust's lint
 infrastructure](../../reference/attributes/diagnostics.md#lint-check-attributes) with
 additional checks for code style, safety, etc. Now let's write a plugin
-[`lint-plugin-test.rs`](https://github.com/rust-lang/rust/blob/master/src/test/ui-fulldeps/auxiliary/lint-plugin-test.rs)
+[`lint-plugin-test.rs`](https://github.com/rust-lang/rust/blob/master/tests/ui-fulldeps/auxiliary/lint-plugin-test.rs)
 that warns about any item named `lintme`.
 
 ```rust,ignore (requires-stage-2)