add informers for AntreaAgentInfos and AntreaControllerInfos

[liu4480]

Describe the problem/challenge you have
I want to monitor AntreaAgentInfos and AntreaControllerInfos to get information about these resources, watch function is not enough since I need to wrap the add/update/delete functions

Describe the solution you'd like
add informer for the two resources

Anything else you would like to add?

[tnqn]

Since this is Antrea resources and we already have its clientset code in the repo, I think harmless to generate the informer in the repo for consuming in case each downstream will have to maintain its own copy, even though Antrea itself doesn't use it yet.
@jianjuns @antoninbas do you agree?

[jianjuns]

Makes sense to me.

[mengdie-song]

Same here, we can generate both informers and listers for AntreaAgentInfos and AntreaControllerInfos, so that others can interact with monitoring CRDs without having to generate informers and listers themselves.

[tnqn]

Thanks @jianjuns @mengdie-song for your inputs.

@liu4480 would you mind creating a PR to add the code you need?

[tnqn]

Closed by #1612