les: fix and slim the unit tests of les (#20247)

* les: loose restriction of unit tests

* les: update unit tests

* les, light: slim the unit tests

les/distributor_test.go

@@ -86,8 +86,8 @@ func (p *testDistPeer) worker(t *testing.T, checkOrder bool, stop chan struct{})
 const (
 	testDistBufLimit       = 10000000
 	testDistMaxCost        = 1000000
-	testDistPeerCount      = 5
-	testDistReqCount       = 5000
+	testDistPeerCount      = 2
+	testDistReqCount       = 10
 	testDistMaxResendCount = 3
 )
 
@@ -128,6 +128,9 @@ func testRequestDistributor(t *testing.T, resend bool) {
 		go peers[i].worker(t, !resend, stop)
 		dist.registerTestPeer(peers[i])
 	}
+	// Disable the mechanism that we will wait a few time for request
+	// even there is no suitable peer to send right now.
+	waitForPeers = 0
 
 	var wg sync.WaitGroup