Add OrcaOobUtil remove listener

[YifeiZhuang]

Required by WRR.

Currently OrcaOobUtil only has setListener(subchannel, listener, config). We need to have a way to remove listener. When the last listener is removed from orca state, stop orca stream.

Option1:

• Add removeListener API

Option2:

• Reuse setListener to remove listener: setListener(subchannel, null, null)

cc. @ejona86

[ejona86]

@YifeiZhuang, can this be closed?

[YifeiZhuang]

#9881