Auto merge of #139720 - petrochenkov:errkind2, r=jieyouxu

compiletest: Make diagnostic kind mandatory on line annotations (take 2)

Compiletest currently accepts line annotations without kind in UI tests.
```
    let a = b + c; //~ my message
```

Such annotations have two effects.
- First, they match any compiler-produced diagnostic kind. This functionality is never used in practice, there are no target-dependent diagnostic kinds of something like that.
- Second, they are not "viral". For example, any explicit `//~ NOTE my msg` in a test requires all other `NOTE` diagnostics in the same test to be annotated. Implicit `//~ my msg` will just match the note and won't require other annotations.

The second functionality has a replacement since recently - directive `//@ dont-require-annotations: NOTE`.

This PR removes support for `//~ my message` and makes the explicit diagnostic kind mandatory.
Unwanted additional annotations are suppressed using the `dont-require-annotations` directive.

Closes rust-lang/compiler-team#862.
Previous attempt - #139427.
r? `@jieyouxu`

Author: bors

src/tests/ui.md

@@ -372,9 +372,9 @@ E.g. use `//@ dont-require-annotations: NOTE` to annotate notes selectively.
 Avoid using this directive for `ERROR`s and `WARN`ings, unless there's a serious reason, like
 target-dependent compiler output.
 
-Missing diagnostic kinds (`//~ message`) are currently accepted, but are being phased away.
-They will match any compiler output kind, but will not force exhaustive annotations for that kind.
-Prefer explicit kind and `//@ dont-require-annotations` to achieve the same effect.
+Some diagnostics are never required to be line-annotated, regardless of their kind or directives,
+for example secondary lines of multiline diagnostics,
+or ubiquitous diagnostics like `aborting due to N previous errors`.
 
 UI tests use the `-A unused` flag by default to ignore all unused warnings, as
 unused warnings are usually not the focus of a test. However, simple code