fix(core): Ensure logs past MAX_LOG_BUFFER_SIZE are not swallowed (#18207)

Looks like we swallowed the log that triggers a flush when
`MAX_LOG_BUFFER_SIZE` is surpassed.

Test demonstrating issue:
[5697b7d](5697b7d)
Fix:
[f7a4d8b](f7a4d8b)

Related metrics pr: #18212
v9 backport: #18213

Author: andreiborza

packages/core/src/logs/internal.ts

@@ -91,14 +91,16 @@ function setLogAttribute(
  */
 export function _INTERNAL_captureSerializedLog(client: Client, serializedLog: SerializedLog): void {
   const bufferMap = _getBufferMap();
-
   const logBuffer = _INTERNAL_getLogBuffer(client);
+
   if (logBuffer === undefined) {
     bufferMap.set(client, [serializedLog]);
   } else {
-    bufferMap.set(client, [...logBuffer, serializedLog]);
     if (logBuffer.length >= MAX_LOG_BUFFER_SIZE) {
       _INTERNAL_flushLogsBuffer(client, logBuffer);
+      bufferMap.set(client, [serializedLog]);
+    } else {
+      bufferMap.set(client, [...logBuffer, serializedLog]);
     }
   }
 }

packages/core/test/lib/logs/internal.test.ts

@@ -259,7 +259,10 @@ describe('_INTERNAL_captureLog', () => {
     // Add one more to trigger flush
     _INTERNAL_captureLog({ level: 'info', message: 'trigger flush' }, scope);
 
-    expect(_INTERNAL_getLogBuffer(client)).toEqual([]);
+    // After flushing the 100 logs, the new log starts a fresh buffer with 1 item
+    const buffer = _INTERNAL_getLogBuffer(client);
+    expect(buffer).toHaveLength(1);
+    expect(buffer?.[0]?.body).toBe('trigger flush');
   });
 
   it('does not flush logs buffer when it is empty', () => {