Add e2e for staking expansion

[gitferry]

[gitferry]

@SebastianElvis is this already tested in

babylon-sdk/tests/e2e/bcd_consumer_integration_test.go

Line 368 in 60d4e54

func (s *BCDConsumerIntegrationTestSuite) Test06MultiStakeToFPs() {

?

[SebastianElvis]

This is not through stake expansion, but rather a normal multi staking request. So it does not seem to resolve this issue

[gitferry]

Right. I'll take this