Refactor x/staking Validation and Delegation tests based on MsgCreateValidator.Pubkey type change. (#7526)

* testing: refactore Validation and Delegation handling of x/staking

This Changeset introduces set of improvements for writing tests.

The idea is to create a testing subpackage which will provide functions
to make tests more dev-friendly and wrap higher level use-cases.
Here is a show-up of of creating a service for staking module
for tests.

This PR also changes the `x/staking/types.MsgCreateValidator.Pubkey` from string
to types.Any. This change motivated the other change to show the pattern I'm describing here.

* add validator checks

* type change fixes

* use deprecated

* adding test slashing

* new network comment update

* working on tests

* Fix TestMsgPkDecode test

* Add UnpackInterfaces to MsgCreateValidator

* Fix tests

* Convert bech32 pubkey to proto

* Fix test

* fix v039/migrate_test/TestMigrate

* fix tests

* testslashing: rename Service to Helper

* file rename

* update TestMsgDecode

Co-authored-by: blushi <marie.gauthier63@gmail.com>
Co-authored-by: Amaury Martiny <amaury.martiny@protonmail.com>
Co-authored-by: Cory Levinson <cjlevinson@gmail.com>

codec/any_test.go

@@ -4,10 +4,9 @@ import (
 	"errors"
 	"testing"
 
-	"github.com/cosmos/cosmos-sdk/codec"
-
 	"github.com/stretchr/testify/require"
 
+	"github.com/cosmos/cosmos-sdk/codec"
 	"github.com/cosmos/cosmos-sdk/codec/types"
 	"github.com/cosmos/cosmos-sdk/testutil/testdata"
 )