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

[petrochenkov]

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

[petrochenkov]

MCP: rust-lang/compiler-team#862, waiting on compiler team.

[petrochenkov]

Most of the diff is due to updated .stderr files.
Technically I could add the //@ dont-require-annotations: NOTE directives to file ends to avoid this, but it really goes against the usual style.

[rustbot]

Some changes occurred in src/tools/compiletest

cc @jieyouxu

[RalfJung]

const ui tets changes LGTM, except that the PR also removes some colons which caught me by surprise as it wasn't mentioned... but if we will unify the colon vs no-colon style soon anyway, it doesn't really matter.

[petrochenkov]

the PR also removes some colons which caught me by surprise as it wasn't mentioned

This is accidental, this PR was converted from #139427 which had some colon changes, and I tried to revert all of them, but apparently missed some. If some more are found during review I'll revert them too.

[tshepang]

would be nice if this also updated rustc-dev-guide

[petrochenkov]

would be nice if this also updated rustc-dev-guide

I'll update, I was waiting for #139618 to land first.

[petrochenkov]

10 days since rust-lang/compiler-team#862 (comment) have passed.
@rustbot author

[rustbot]

Reminder, once the PR becomes ready for a review, use @rustbot ready.

[rustbot]

The rustc-dev-guide subtree was changed. If this PR only touches the dev guide consider submitting a PR directly to rust-lang/rustc-dev-guide otherwise thank you for updating the dev guide with your changes.

cc @BoxyUwU, @jieyouxu, @Kobzol

[petrochenkov]

@rustbot ready