Use project-relative path when calculating gitlab message fingerprint (#11532)

## Summary

Concurrent GitLab runners clone projects into separate directories, e.g.
`{builds_dir}/$RUNNER_TOKEN_KEY/$CONCURRENT_ID/$NAMESPACE/$PROJECT_NAME`.
Since the fingerprint uses the full path to the file, the fingerprints
calculated by Ruff are different depending on which concurrent runner it
executes on, so often an MR will appear to remove all existing issues
and add them with new fingerprints.

I've adjusted the fingerprint function to use the project relative path,
which fixes this. Unfortunately this will have a breaking change for any
current users of this output - the fingerprints will change and appear
in GitLab as all linting messages having been fixed and then created.

## Test Plan

`cargo nextest run`

Running `ruff check --output-format gitlab` in a git repo, moving the
repo and running again, verifying no diffs between the outputs

crates/ruff_linter/src/message/gitlab.rs

@@ -82,12 +82,12 @@ impl Serialize for SerializedMessages<'_> {
                 |project_dir| relativize_path_to(message.filename(), project_dir),
             );
 
-            let mut message_fingerprint = fingerprint(message, 0);
+            let mut message_fingerprint = fingerprint(message, &path, 0);
 
             // Make sure that we do not get a fingerprint that is already in use
             // by adding in the previously generated one.
             while fingerprints.contains(&message_fingerprint) {
-                message_fingerprint = fingerprint(message, message_fingerprint);
+                message_fingerprint = fingerprint(message, &path, message_fingerprint);
             }
             fingerprints.insert(message_fingerprint);
 
@@ -109,12 +109,12 @@ impl Serialize for SerializedMessages<'_> {
 }
 
 /// Generate a unique fingerprint to identify a violation.
-fn fingerprint(message: &Message, salt: u64) -> u64 {
+fn fingerprint(message: &Message, project_path: &str, salt: u64) -> u64 {
     let Message {
         kind,
         range: _,
         fix: _fix,
-        file,
+        file: _,
         noqa_offset: _,
     } = message;
 
@@ -122,7 +122,7 @@ fn fingerprint(message: &Message, salt: u64) -> u64 {
 
     salt.hash(&mut hasher);
     kind.name.hash(&mut hasher);
-    file.name().hash(&mut hasher);
+    project_path.hash(&mut hasher);
 
     hasher.finish()
 }