Combine OldDiagnostic and Diagnostic (#19053)

## Summary

This PR is a collaboration with @AlexWaygood from our pairing session
last Friday.

The main goal here is removing `ruff_linter::message::OldDiagnostic` in
favor of
using `ruff_db::diagnostic::Diagnostic` directly. This involved a few
major steps:

- Transferring the fields
- Transferring the methods and trait implementations, where possible
- Converting some constructor methods to free functions
- Moving the `SecondaryCode` struct
- Updating the method names

I'm hoping that some of the methods, especially those in the
`expect_ruff_*`
family, won't be necessary long-term, but I avoided trying to replace
them
entirely for now to keep the already-large diff a bit smaller.

### Related refactors

Alex and I noticed a few refactoring opportunities while looking at the
code,
specifically the very similar implementations for
`create_parse_diagnostic`,
`create_unsupported_syntax_diagnostic`, and
`create_semantic_syntax_diagnostic`.
We combined these into a single generic function, which I then copied
into
`ruff_linter::message` with some small changes and a TODO to combine
them in the
future.

I also deleted the `DisplayParseErrorType` and `TruncateAtNewline` types
for
reporting parse errors. These were added in #4124, I believe to work
around the
error messages from LALRPOP. Removing these didn't affect any tests, so
I think
they were unnecessary now that we fully control the error messages from
the
parser.

On a more minor note, I factored out some calls to the
`OldDiagnostic::filename`
(now `Diagnostic::expect_ruff_filename`) function to avoid repeatedly
allocating
`String`s in some places.

### Snapshot changes

The `show_statistics_syntax_errors` integration test changed because the
`OldDiagnostic::name` method used `syntax-error` instead of
`invalid-syntax`
like in ty. I think this (`--statistics`) is one of the only places we
actually
use this name for syntax errors, so I hope this is okay. An alternative
is to
use `syntax-error` in ty too.

The other snapshot changes are from removing this code, as discussed on

[Discord](1388252408):


34052a1185/crates/ruff_linter/src/message/mod.rs (L128-L135)

I think both of these are technically breaking changes, but they only
affect
syntax errors and are very narrow in scope, while also pretty
substantially
simplifying the refactor, so I hope they're okay to include in a patch
release.

## Test plan

Existing tests, with the adjustments mentioned above

---------

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

crates/ruff_linter/src/codes.rs

@@ -4,6 +4,7 @@
 /// `--select`. For pylint this is e.g. C0414 and E0118 but also C and E01.
 use std::fmt::Formatter;
 
+use ruff_db::diagnostic::SecondaryCode;
 use strum_macros::EnumIter;
 
 use crate::registry::Linter;
@@ -52,6 +53,18 @@ impl PartialEq<NoqaCode> for &str {
     }
 }
 
+impl PartialEq<NoqaCode> for SecondaryCode {
+    fn eq(&self, other: &NoqaCode) -> bool {
+        &self.as_str() == other
+    }
+}
+
+impl PartialEq<SecondaryCode> for NoqaCode {
+    fn eq(&self, other: &SecondaryCode) -> bool {
+        other.eq(self)
+    }
+}
+
 impl serde::Serialize for NoqaCode {
     fn serialize<S>(&self, serializer: S) -> std::result::Result<S::Ok, S::Error>
     where