fix(core): Stop sending client reports for breadcrumbs (#24537)

This PR removes the `{ reason: 'buffer_overflow', category: 'log_item'
}` client report the SDK sent when the breadcrumbs buffer (100
breadcrumbs limit) overflowed and we evicted breadcrumbs.

Why? When we started working on logs, we [wanted to
know](getsentry/team-sdks#116) how many
breadcrumbs we currently discard due to the 100 crumbs limit. We used
the new `log_item` data category for this and `buffer_overflow` reason.
Later on, we added client reports for actual log discards and re-used
this data category but sent different reasons. Meaning different
telemtry items now fall into the same discard bucket as reported in
#24510.

Since I don't think we still need to know about breadcrumb discards, and
they're not their own telemetry items but part of errror and transaction
events, I think we can just stop emitting client reports for them.

closes #24510

Author: Lms24

packages/core/src/scope.ts

@@ -574,7 +574,6 @@ export class Scope {
     this._breadcrumbs.push(mergedBreadcrumb);
     if (this._breadcrumbs.length > maxCrumbs) {
       this._breadcrumbs = this._breadcrumbs.slice(-maxCrumbs);
-      this._client?.recordDroppedEvent('buffer_overflow', 'log_item');
     }
 
     this._notifyScopeListeners();

packages/core/test/lib/client.test.ts

@@ -357,22 +357,6 @@ describe('Client', () => {
       expect(isolationScopeBreadcrumbs).toEqual([{ message: 'hello3', timestamp: expect.any(Number) }]);
     });
 
-    test('it records `buffer_overflow` client discard reason when buffer overflows', () => {
-      const options = getDefaultTestClientOptions({ maxBreadcrumbs: 1 });
-      const client = new TestClient(options);
-      const recordLostEventSpy = vi.spyOn(client, 'recordDroppedEvent');
-      setCurrentClient(client);
-      getIsolationScope().setClient(client);
-      client.init();
-
-      addBreadcrumb({ message: 'hello1' });
-      addBreadcrumb({ message: 'hello2' });
-      addBreadcrumb({ message: 'hello3' });
-
-      expect(recordLostEventSpy).toHaveBeenCalledTimes(2);
-      expect(recordLostEventSpy).toHaveBeenLastCalledWith('buffer_overflow', 'log_item');
-    });
-
     test('calls `beforeBreadcrumb` and adds the breadcrumb without any changes', () => {
       const beforeBreadcrumb = vi.fn(breadcrumb => breadcrumb);
       const options = getDefaultTestClientOptions({ beforeBreadcrumb });