cmd, core, eth/tracers: support fancier js tracing (#15516)

* cmd, core, eth/tracers: support fancier js tracing

* eth, internal/web3ext: rework trace API, concurrency, chain tracing

* eth/tracers: add three more JavaScript tracers

* eth/tracers, vendor: swap ottovm to duktape for tracing

* core, eth, internal: finalize call tracer and needed extras

* eth, tests: prestate tracer, call test suite, rewinding

* vendor: fix windows builds for tracer js engine

* vendor: temporary duktape fix

* eth/tracers: fix up 4byte and evmdis tracer

* vendor: pull in latest duktape with my upstream fixes

* eth: fix some review comments

* eth: rename rewind to reexec to make it more obvious

* core/vm: terminate tracing using defers

ethdb/memory_database.go

@@ -37,6 +37,12 @@ func NewMemDatabase() (*MemDatabase, error) {
 	}, nil
 }
 
+func NewMemDatabaseWithCap(size int) (*MemDatabase, error) {
+	return &MemDatabase{
+		db: make(map[string][]byte, size),
+	}, nil
+}
+
 func (db *MemDatabase) Put(key []byte, value []byte) error {
 	db.lock.Lock()
 	defer db.lock.Unlock()
@@ -74,14 +80,6 @@ func (db *MemDatabase) Keys() [][]byte {
 	return keys
 }
 
-/*
-func (db *MemDatabase) GetKeys() []*common.Key {
-	data, _ := db.Get([]byte("KeyRing"))
-
-	return []*common.Key{common.NewKeyFromBytes(data)}
-}
-*/
-
 func (db *MemDatabase) Delete(key []byte) error {
 	db.lock.Lock()
 	defer db.lock.Unlock()
@@ -96,6 +94,8 @@ func (db *MemDatabase) NewBatch() Batch {
 	return &memBatch{db: db}
 }
 
+func (db *MemDatabase) Len() int { return len(db.db) }
+
 type kv struct{ k, v []byte }
 
 type memBatch struct {