core/vm: use uint256 in EVM implementation (#20787)

* core/vm: use fixed uint256 library instead of big

* core/vm: remove intpools

* core/vm: upgrade uint256, fixes uint256.NewFromBig

* core/vm: use uint256.Int by value in Stack

* core/vm: upgrade uint256 to v1.0.0

* core/vm: don't preallocate space for 1024 stack items (only 16)

Co-authored-by: Martin Holst Swende <martin@swende.se>

core/vm/interpreter.go

@@ -84,8 +84,6 @@ type EVMInterpreter struct {
 	evm *EVM
 	cfg Config
 
-	intPool *intPool
-
 	hasher    keccakState // Keccak256 hasher instance shared across opcodes
 	hasherBuf common.Hash // Keccak256 hasher result array shared aross opcodes
 
@@ -141,13 +139,6 @@ func NewEVMInterpreter(evm *EVM, cfg Config) *EVMInterpreter {
 // considered a revert-and-consume-all-gas operation except for
 // ErrExecutionReverted which means revert-and-keep-gas-left.
 func (in *EVMInterpreter) Run(contract *Contract, input []byte, readOnly bool) (ret []byte, err error) {
-	if in.intPool == nil {
-		in.intPool = poolOfIntPools.get()
-		defer func() {
-			poolOfIntPools.put(in.intPool)
-			in.intPool = nil
-		}()
-	}
 
 	// Increment the call depth which is restricted to 1024
 	in.evm.depth++
@@ -193,9 +184,6 @@ func (in *EVMInterpreter) Run(contract *Contract, input []byte, readOnly bool) (
 	)
 	contract.Input = input
 
-	// Reclaim the stack as an int pool when the execution stops
-	defer func() { in.intPool.put(stack.data...) }()
-
 	if in.cfg.Debug {
 		defer func() {
 			if err != nil {
@@ -290,11 +278,6 @@ func (in *EVMInterpreter) Run(contract *Contract, input []byte, readOnly bool) (
 
 		// execute the operation
 		res, err = operation.execute(&pc, in, callContext)
-		// verifyPool is a build flag. Pool verification makes sure the integrity
-		// of the integer pool by comparing values to a default value.
-		if verifyPool {
-			verifyIntegerPool(in.intPool)
-		}
 		// if the operation clears the return data (e.g. it has returning data)
 		// set the last return to the result of the operation.
 		if operation.returns {