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>

testutil/network/network.go

@@ -162,6 +162,7 @@ type (
 	}
 )
 
+// New creates a new Network for integration tests.
 func New(t *testing.T, cfg Config) *Network {
 	// only one caller/test can create and use a network at a time
 	t.Log("acquiring test network lock")
@@ -293,7 +294,7 @@ func New(t *testing.T, cfg Config) *Network {
 		commission, err := sdk.NewDecFromStr("0.5")
 		require.NoError(t, err)
 
-		createValMsg := stakingtypes.NewMsgCreateValidator(
+		createValMsg, err := stakingtypes.NewMsgCreateValidator(
 			sdk.ValAddress(addr),
 			valPubKeys[i],
 			sdk.NewCoin(sdk.DefaultBondDenom, cfg.BondedTokens),
@@ -301,6 +302,7 @@ func New(t *testing.T, cfg Config) *Network {
 			stakingtypes.NewCommissionRates(commission, sdk.OneDec(), sdk.OneDec()),
 			sdk.OneInt(),
 		)
+		require.NoError(t, err)
 
 		p2pURL, err := url.Parse(p2pAddr)
 		require.NoError(t, err)