crypto/merkle: remove simple prefix (#4989)

## Description

This PR removes simple prefix from all types in the crypto/merkle directory.

The two proto types `Proof` & `ProofOp` have been moved to the `proto/crypto/merkle` directory.

proto messge `Proof` was renamed to `ProofOps` and `SimpleProof` message to `Proof`. 

Closes: #2755

crypto/armor/armor_test.go

@@ -7,7 +7,7 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-func TestSimpleArmor(t *testing.T) {
+func TestArmor(t *testing.T) {
 	blockType := "MINT TEST"
 	data := []byte("somedata")
 	armorStr := EncodeArmor(blockType, nil, data)