Improve CLI tests assertions

[nullpointer0x00]

Summary

The cli tests assertions can be improved. We have this pattern all throughout our code and would be nice to have it all cleaned up at once to have consistency and a proper example to base new tests off of.

A few things:

testCases := []struct {
		name         string
		cmd          *cobra.Command
		args         []string
		expectErr    bool
		respType     proto.Message
		expectedCode uint32
	}

....

		s.Run(tc.name, func() {
			clientCtx := s.testnet.Validators[0].ClientCtx
			out, err := clitestutil.ExecTestCLICmd(clientCtx, tc.cmd, tc.args)

			if tc.expectErr {
				s.Require().Error(err)
			} else {
				s.Require().NoError(err)
				s.Require().NoError(clientCtx.Codec.UnmarshalJSON(out.Bytes(), tc.respType), out.String())
				txResp := tc.respType.(*sdk.TxResponse)
				s.Require().Equal(tc.expectedCode, txResp.Code)
			}
		})
	}

1.) We have an expectedErr bool. This should be a string and and checked with EqualError call.
2.) Don't need the respType property, because the response is always sdk.TxResponse
3.) s.Require().NoError(clientCtx.Codec.UnmarshalJSON(out.Bytes(), tc.respType), out.String()) Fix output message.
4.) Change expected code checks to int32 instead of uint32 and add output message.

Problem Definition

Proposal

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[SpicyLemon]

A couple other notes here:

1. The out variable there (1st returned variable from ExecTestCLICmd) is a buffer, and calling either Bytes() or String() on it might clear it out so that the next time one of those are called, it returns empty. So it's better to call one of those and store it in a variable for use down the road. It's an easy cast to go between the two string and []byte types later.
2. We now have the TxExecutor (defined in testutil/cli/exec.go) that we should consider switching to for these tests.