libs/common: Refactor libs/common 4 (#4237)

* libs/common: Refactor libs/common 4

- move byte function out of cmn to its own pkg
- move tempfile out of cmn to its own pkg
- move throttletimer to its own pkg

ref #4147

Signed-off-by: Marko Baricevic <marbar3778@yahoo.com>

* add changelog entry

* fix linting issues

types/tx.go

@@ -10,7 +10,7 @@ import (
 	abci "github.com/tendermint/tendermint/abci/types"
 	"github.com/tendermint/tendermint/crypto/merkle"
 	"github.com/tendermint/tendermint/crypto/tmhash"
-	cmn "github.com/tendermint/tendermint/libs/common"
+	tmbytes "github.com/tendermint/tendermint/libs/bytes"
 )
 
 // Tx is an arbitrary byte array.
@@ -83,7 +83,7 @@ func (txs Txs) Proof(i int) TxProof {
 
 // TxProof represents a Merkle proof of the presence of a transaction in the Merkle tree.
 type TxProof struct {
-	RootHash cmn.HexBytes       `json:"root_hash"`
+	RootHash tmbytes.HexBytes   `json:"root_hash"`
 	Data     Tx                 `json:"data"`
 	Proof    merkle.SimpleProof `json:"proof"`
 }