cmd, core, eth, light, trie: add trie read caching layer

vendor/github.com/allegro/bigcache/hash.go

@@ -0,0 +1,8 @@
+package bigcache
+
+// Hasher is responsible for generating unsigned, 64 bit hash of provided string. Hasher should minimize collisions
+// (generating same hash for different strings) and while performance is also important fast functions are preferable (i.e.
+// you can use FarmHash family).
+type Hasher interface {
+	Sum64(string) uint64
+}