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`rand.Read` has been replaced by `crypto/rand`.`Read` in this PR.

core/state/snapshot/difflayer_test.go

@@ -18,6 +18,7 @@ package snapshot
 
 import (
 	"bytes"
+	crand "crypto/rand"
 	"math/rand"
 	"testing"
 
@@ -73,7 +74,7 @@ func TestMergeBasics(t *testing.T) {
 		if rand.Intn(2) == 0 {
 			accStorage := make(map[common.Hash][]byte)
 			value := make([]byte, 32)
-			rand.Read(value)
+			crand.Read(value)
 			accStorage[randomHash()] = value
 			storage[h] = accStorage
 		}
@@ -294,7 +295,7 @@ func BenchmarkSearchSlot(b *testing.B) {
 		accStorage := make(map[common.Hash][]byte)
 		for i := 0; i < 5; i++ {
 			value := make([]byte, 32)
-			rand.Read(value)
+			crand.Read(value)
 			accStorage[randomHash()] = value
 			storage[accountKey] = accStorage
 		}
@@ -330,7 +331,7 @@ func BenchmarkFlatten(b *testing.B) {
 			accStorage := make(map[common.Hash][]byte)
 			for i := 0; i < 20; i++ {
 				value := make([]byte, 32)
-				rand.Read(value)
+				crand.Read(value)
 				accStorage[randomHash()] = value
 			}
 			storage[accountKey] = accStorage
@@ -379,7 +380,7 @@ func BenchmarkJournal(b *testing.B) {
 			accStorage := make(map[common.Hash][]byte)
 			for i := 0; i < 200; i++ {
 				value := make([]byte, 32)
-				rand.Read(value)
+				crand.Read(value)
 				accStorage[randomHash()] = value
 			}
 			storage[accountKey] = accStorage

core/state/snapshot/iterator_test.go

@@ -18,6 +18,7 @@ package snapshot
 
 import (
 	"bytes"
+	crand "crypto/rand"
 	"encoding/binary"
 	"fmt"
 	"math/rand"
@@ -47,7 +48,7 @@ func TestAccountIteratorBasics(t *testing.T) {
 		if rand.Intn(2) == 0 {
 			accStorage := make(map[common.Hash][]byte)
 			value := make([]byte, 32)
-			rand.Read(value)
+			crand.Read(value)
 			accStorage[randomHash()] = value
 			storage[h] = accStorage
 		}
@@ -79,7 +80,7 @@ func TestStorageIteratorBasics(t *testing.T) {
 
 		var nilstorage int
 		for i := 0; i < 100; i++ {
-			rand.Read(value)
+			crand.Read(value)
 			if rand.Intn(2) == 0 {
 				accStorage[randomHash()] = common.CopyBytes(value)
 			} else {

core/state/snapshot/snapshot_test.go

@@ -17,6 +17,7 @@
 package snapshot
 
 import (
+	crand "crypto/rand"
 	"encoding/binary"
 	"fmt"
 	"math/big"
@@ -33,7 +34,7 @@ import (
 // randomHash generates a random blob of data and returns it as a hash.
 func randomHash() common.Hash {
 	var hash common.Hash
-	if n, err := rand.Read(hash[:]); n != common.HashLength || err != nil {
+	if n, err := crand.Read(hash[:]); n != common.HashLength || err != nil {
 		panic(err)
 	}
 	return hash