Update to latest kuberesolver

[gouthamve]

@tomwilkie @bboreham

[bboreham]

Are there any notable bug fixes or feature changes in this version?

[gouthamve]

Nope, but it uses the new gRPC API for loadblancing. It's just the updated version of the previous library.

[bboreham]

Review might go faster if you say what is going on in the 80-odd lines of changes.

[gouthamve]

Previously, we needed to pass in a resolver as an option. And the resolver used to do both resolution and loadbalancing, afaik.

Now, the API changed to "registering" resolvers. i.e, mapping scheme to resolvers, for example kubernetes:// --> kuberesolver, dns:// --> dns resolver, etc. And then specifying the load-balancing policy via the resolution mechanism or manually or via an grpclb, etc.

See: https://github.com/grpc/proposal/blob/master/L9-go-resolver-balancer-API.md

In this PR, I modified our client creation to use the new API through kuberesolver v2. It was fairly straightforward, needed to remove the additional resolver dial option and needed to specify the loadbalancing.

[tomwilkie]

I was also hoping that kuberesolver v2 would fix sercand/kuberesolver#4, but it doesn't appear to.

[bboreham]

Thanks!

[bboreham]

for example kubernetes:// --> kuberesolver, dns:// --> dns resolver, etc.

According to https://github.com/grpc/grpc-go/blob/v1.19.0/clientconn.go#L125 those should have three slashes. Did you test this code?

[gouthamve]

Oh right, we ended up using dns:/// which worked. Though let me update the code to make it :///