all: remove deprecated uses of math.rand (#26710)

This PR is a (superior) alternative to https://github.com/ethereum/go-ethereum/pull/26708, it handles deprecation, primarily two specific cases. 

`rand.Seed` is typically used in two ways
- `rand.Seed(time.Now().UnixNano())` -- we seed it, just to be sure to get some random, and not always get the same thing on every run. This is not needed, with global seeding, so those are just removed. 
- `rand.Seed(1)` this is typically done to ensure we have a stable test. If we rely on this, we need to fix up the tests to use a deterministic prng-source. A few occurrences like this has been replaced with a proper custom source. 

`rand.Read` has been replaced by `crypto/rand`.`Read` in this PR.

les/api_test.go

@@ -18,6 +18,7 @@ package les
 
 import (
 	"context"
+	crand "crypto/rand"
 	"errors"
 	"flag"
 	"math/rand"
@@ -326,7 +327,7 @@ func getHead(ctx context.Context, t *testing.T, client *rpc.Client) (uint64, com
 func testRequest(ctx context.Context, t *testing.T, client *rpc.Client) bool {
 	var res string
 	var addr common.Address
-	rand.Read(addr[:])
+	crand.Read(addr[:])
 	c, cancel := context.WithTimeout(ctx, time.Second*12)
 	defer cancel()
 	err := client.CallContext(c, &res, "eth_getBalance", addr, "latest")

les/benchmark.go

@@ -17,6 +17,7 @@
 package les
 
 import (
+	crand "crypto/rand"
 	"encoding/binary"
 	"fmt"
 	"math/big"
@@ -114,7 +115,7 @@ func (b *benchmarkProofsOrCode) init(h *serverHandler, count int) error {
 
 func (b *benchmarkProofsOrCode) request(peer *serverPeer, index int) error {
 	key := make([]byte, 32)
-	rand.Read(key)
+	crand.Read(key)
 	if b.code {
 		return peer.requestCode(0, []CodeReq{{BHash: b.headHash, AccKey: key}})
 	}
@@ -176,7 +177,7 @@ func (b *benchmarkTxSend) init(h *serverHandler, count int) error {
 
 	for i := range b.txs {
 		data := make([]byte, txSizeCostLimit)
-		rand.Read(data)
+		crand.Read(data)
 		tx, err := types.SignTx(types.NewTransaction(0, addr, new(big.Int), 0, new(big.Int), data), signer, key)
 		if err != nil {
 			panic(err)
@@ -200,7 +201,7 @@ func (b *benchmarkTxStatus) init(h *serverHandler, count int) error {
 
 func (b *benchmarkTxStatus) request(peer *serverPeer, index int) error {
 	var hash common.Hash
-	rand.Read(hash[:])
+	crand.Read(hash[:])
 	return peer.requestTxStatus(0, []common.Hash{hash})
 }
 
@@ -278,7 +279,7 @@ func (h *serverHandler) measure(setup *benchmarkSetup, count int) error {
 	clientMeteredPipe := &meteredPipe{rw: clientPipe}
 	serverMeteredPipe := &meteredPipe{rw: serverPipe}
 	var id enode.ID
-	rand.Read(id[:])
+	crand.Read(id[:])
 
 	peer1 := newServerPeer(lpv2, NetworkId, false, p2p.NewPeer(id, "client", nil), clientMeteredPipe)
 	peer2 := newClientPeer(lpv2, NetworkId, p2p.NewPeer(id, "server", nil), serverMeteredPipe)

les/utils/limiter_test.go

@@ -17,7 +17,7 @@
 package utils
 
 import (
-	"math/rand"
+	"crypto/rand"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/p2p/enode"

les/vflux/client/fillset_test.go

@@ -17,7 +17,7 @@
 package client
 
 import (
-	"math/rand"
+	"crypto/rand"
 	"testing"
 	"time"
 

les/vflux/server/clientpool_test.go

@@ -135,7 +135,6 @@ func alwaysTrueFn() bool {
 }
 
 func testClientPool(t *testing.T, activeLimit, clientCount, paidCount int, randomDisconnect bool) {
-	rand.Seed(time.Now().UnixNano())
 	var (
 		clock     mclock.Simulated
 		db        = rawdb.NewMemoryDatabase()