[testbed] increase timeout values in large file tests (open-telemetry#35054)

See
open-telemetry#35053 (comment)

**Link to tracking Issue:**
open-telemetry#35053

Author: VihasMakwana

testbed/tests/log_test.go

@@ -345,7 +345,7 @@ func TestLargeFileOnce(t *testing.T) {
 	tc.StartBackend()
 	tc.StartAgent()
 
-	tc.WaitForN(func() bool { return dataItemsGenerated.Load() == tc.MockBackend.DataItemsReceived() }, 20*time.Second, "all logs received")
+	tc.WaitForN(func() bool { return dataItemsGenerated.Load() == tc.MockBackend.DataItemsReceived() }, 200*time.Second, "all logs received")
 
 	tc.StopAgent()
 	tc.ValidateData()

testbed/tests/scenarios.go

@@ -542,7 +542,7 @@ func ScenarioLong(
 
 	tc.StopLoad()
 
-	tc.WaitFor(func() bool { return tc.LoadGenerator.DataItemsSent() == tc.MockBackend.DataItemsReceived() }, "all logs received")
+	tc.WaitForN(func() bool { return tc.LoadGenerator.DataItemsSent() == tc.MockBackend.DataItemsReceived() }, 60*time.Second, "all logs received")
 
 	tc.ValidateData()
 }