gometalinter -> golangci-lint migration (#3933)

{,scripts/}Makefile:
- Remove gometalinter, install golangci-lint.
- Remove distinction between tools and devtools.
  Just tools is enough.
- test_lint -> lint
  Migrating away from underscore separated names.
- Remove unnecessary targets.
- Drop tendermint/lint. Incompatbile with golangci-lint
  and no longer necessary anyway.
- Fix misleading message in go-mod-cache.
- New ci-target to avoid download tools twice.
- Run tests with -mod=readonly.

Port tools/gometalinter.json to .golangci.yml
Update CircleCI config accordingly.

Closes: #3896

client/keys/types.go

@@ -11,6 +11,17 @@ type AddNewKey struct {
 	Index    int    `json:"index,string,omitempty"`
 }
 
+// NewAddNewKey constructs a new AddNewKey request structure.
+func NewAddNewKey(name, password, mnemonic string, account, index int) AddNewKey {
+	return AddNewKey{
+		Name:     name,
+		Password: password,
+		Mnemonic: mnemonic,
+		Account:  account,
+		Index:    index,
+	}
+}
+
 // RecoverKeyBody recovers a key
 type RecoverKey struct {
 	Password string `json:"password"`
@@ -19,13 +30,26 @@ type RecoverKey struct {
 	Index    int    `json:"index,string,omitempty"`
 }
 
+// NewRecoverKey constructs a new RecoverKey request structure.
+func NewRecoverKey(password, mnemonic string, account, index int) RecoverKey {
+	return RecoverKey{Password: password, Mnemonic: mnemonic, Account: account, Index: index}
+}
+
 // UpdateKeyReq requests updating a key
 type UpdateKeyReq struct {
 	OldPassword string `json:"old_password"`
 	NewPassword string `json:"new_password"`
 }
 
+// NewUpdateKeyReq constructs a new UpdateKeyReq structure.
+func NewUpdateKeyReq(old, new string) UpdateKeyReq {
+	return UpdateKeyReq{OldPassword: old, NewPassword: new}
+}
+
 // DeleteKeyReq requests deleting a key
 type DeleteKeyReq struct {
 	Password string `json:"password"`
 }
+
+// NewDeleteKeyReq constructs a new DeleteKeyReq structure.
+func NewDeleteKeyReq(password string) DeleteKeyReq { return DeleteKeyReq{Password: password} }