core, eth: split eth package, implement snap protocol (#21482)

This commit splits the eth package, separating the handling of eth and snap protocols. It also includes the capability to run snap sync (https://github.com/ethereum/devp2p/blob/master/caps/snap.md) , but does not enable it by default. 

Co-authored-by: Marius van der Wijden <m.vanderwijden@live.de>
Co-authored-by: Martin Holst Swende <martin@swende.se>

eth/api_test.go

@@ -57,6 +57,8 @@ func (h resultHash) Swap(i, j int)      { h[i], h[j] = h[j], h[i] }
 func (h resultHash) Less(i, j int) bool { return bytes.Compare(h[i].Bytes(), h[j].Bytes()) < 0 }
 
 func TestAccountRange(t *testing.T) {
+	t.Parallel()
+
 	var (
 		statedb  = state.NewDatabaseWithConfig(rawdb.NewMemoryDatabase(), nil)
 		state, _ = state.New(common.Hash{}, statedb, nil)
@@ -126,6 +128,8 @@ func TestAccountRange(t *testing.T) {
 }
 
 func TestEmptyAccountRange(t *testing.T) {
+	t.Parallel()
+
 	var (
 		statedb  = state.NewDatabase(rawdb.NewMemoryDatabase())
 		state, _ = state.New(common.Hash{}, statedb, nil)
@@ -142,6 +146,8 @@ func TestEmptyAccountRange(t *testing.T) {
 }
 
 func TestStorageRangeAt(t *testing.T) {
+	t.Parallel()
+
 	// Create a state where account 0x010000... has a few storage entries.
 	var (
 		state, _ = state.New(common.Hash{}, state.NewDatabase(rawdb.NewMemoryDatabase()), nil)