lite2: move AutoClient into Client (#4326)

* lite2: move AutoClient into Client

Most of the users will want auto update feature, so it makes sense to
move it into the Client itself, rather than having a separate
abstraction (it makes the code cleaner, but introduces an extra thing
the user will need to learn).

Also, add `FirstTrustedHeight` func to Client to get first trusted height.

* fix db store tests

* separate examples for auto and manual clients

* AutoUpdate tries to update to latest state

NOT 1 header at a time

* fix errors

* lite2: make Logger an option

remove SetLogger func

* fix lite cmd

* lite2: make concurrency assumptions explicit

* fixes after my own review

* no need for nextHeightFn

sequence func will download intermediate headers

* correct comment

cmd/tendermint/commands/lite.go

@@ -86,11 +86,11 @@ func runProxy(cmd *cobra.Command, args []string) error {
 		},
 		httpp.NewWithClient(chainID, node),
 		dbs.New(db, chainID),
+		lite.Logger(liteLogger),
 	)
 	if err != nil {
 		return err
 	}
-	c.SetLogger(liteLogger)
 
 	p := lproxy.Proxy{
 		Addr:   listenAddr,