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 !

Author: bors

tests/ui/crashes/ice-6254.rs

@@ -1,4 +1,4 @@
-// originally from ./src/test/ui/pattern/usefulness/consts-opaque.rs
+// originally from ./tests/ui/pattern/usefulness/consts-opaque.rs
 // panicked at 'assertion failed: rows.iter().all(|r| r.len() == v.len())',
 // compiler/rustc_mir_build/src/thir/pattern/_match.rs:2030:5
 

tests/ui/crashes/ice-6255.rs

@@ -1,4 +1,4 @@
-// originally from rustc ./src/test/ui/macros/issue-78325-inconsistent-resolution.rs
+// originally from rustc ./tests/ui/macros/issue-78325-inconsistent-resolution.rs
 // inconsistent resolution for a macro
 
 macro_rules! define_other_core {

tests/ui/crashes/ice-6256.rs

@@ -1,4 +1,4 @@
-// originally from rustc ./src/test/ui/regions/issue-78262.rs
+// originally from rustc ./tests/ui/regions/issue-78262.rs
 // ICE: to get the signature of a closure, use substs.as_closure().sig() not fn_sig()
 #![allow(clippy::upper_case_acronyms)]