Implement a crosschain consensus breaking change test

[lumtis]

Describe the Issue
Some ZetaClient only upgrade, where the consensus breaking test would pass, would still break cctx processing.

Example: change in the outbound creation logic block the signing until enough ZetaClient upgrade the change.

When this happen the ZetaClient upgrade process should be more coordinated compare to if there is no breaking changes between upgrade.

In many case, we could determine manually if the change is crosschain consensus breaking, however a E2E test would simplify the process and allow us to remind when a coordinated release is necessary.

Currently the consensus breaking change pass with these change because a single signer is enought to sign outbound transaction.
For the crosschain consenssu breaking change, a change in the parameter should be performed, or more observer-signer should be added so that we can check if cctx are blocked or not.

[gartnera]

The easiest way to do this right now is to increase to 4 zetaclients on the consensus tests with 3 being on the old version. The threshold is a hardcoded function in go-tss (conversion.GetThreshold())

func TestGetThreshold(t *testing.T) {
	testCases := []struct {
		name          string
		partyNum      int
		wantThreshold int
		wantErr       error
	}{
		{
			name:          "2 parties should have threshold 1",
			partyNum:      2,
			wantThreshold: 1,
			wantErr:       nil,
		},
		{
			name:          "3 parties should have threshold 1",
			partyNum:      3,
			wantThreshold: 1,
			wantErr:       nil,
		},
		{
			name:          "4 parties should have threshold 2",
			partyNum:      4,
			wantThreshold: 2,
			wantErr:       nil,
		},
		{
			name:          "9 parties should have threshold 5",
			partyNum:      9,
			wantThreshold: 5,
			wantErr:       nil,
		},
	}

	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			got, err := GetThreshold(tc.partyNum)
			if err != tc.wantErr {
				t.Fatalf("GetThreshold(%d) got error %v, want %v", tc.partyNum, err, tc.wantErr)
			}
			if got != tc.wantThreshold {
				t.Errorf("GetThreshold(%d) = %d, want %d", tc.partyNum, got, tc.wantThreshold)
			}
		})
	}
}

The slightly better but more complicated way would be to add the ability to override the threshold on keygen