go mod: update grpc module to latest 1.59.0

[mdibaiee]

See grpc/grpc-go#645

This change is 

[jgraettinger]

I'm definitely in favor of updating, but this first needs to be fully reconciled with #335

I don't have a handle on the API changes for gRPC balancers or the implications of updating, and we would need to verify all that first.

[mdibaiee]

Changelog from 1.40.0 to 1.59.0 with notable behaviour changes:

• 1.41.0
  • balancer: SubConns no longer automatically reconnect after READY; instead they transition to IDLE on connection loss (clientconn: do not automatically reconnect addrConns; go idle instead grpc/grpc-go#4613)
    • this change is already addressed by align with grpc base/balancer to trigger reconnect in Idle state (when we move to gRPC 1.41+) #335
• 1.42.0
• 1.43.0
• 1.44.0
• 1.45.0
• 1.46.0
  • client: change connectivity state to TransientFailure in pick_first LB policy when all addresses are removed (grpc: move to TransientFailure in pick_first LB policy when all addresses are removed grpc/grpc-go#5274)
    • This is a minor change that brings grpc-go's behavior in line with the intended behavior and how C and Java behave.
• 1.47.0
• 1.48.0
• 1.49.0
• 1.50.0
• 1.51.0
• 1.52.0
• 1.53.0
• 1.54.0
• 1.55.0
• 1.56.0
• 1.57.0
• 1.58.0
  • balancer: add StateListener to NewSubConnOptions for SubConn state updates and deprecate Balancer.UpdateSubConnState (balancer: add StateListener to NewSubConnOptions for SubConn state updates grpc/grpc-go#6481)
    • UpdateSubConnState will be deleted in the future.
  • balancer: add SubConn.Shutdown and deprecate Balancer.RemoveSubConn (balancer: add SubConn.Shutdown; deprecate Balancer.RemoveSubConn grpc/grpc-go#6493)
    • RemoveSubConn will be deleted in the future.
  • resolver: remove deprecated AddressType (resolver: remove deprecated AddressType grpc/grpc-go#6451)
    • This was previously used as a signal to enable the "grpclb" load balancing policy, and to pass LB addresses to the policy. Instead, balancer/grpclb/state.Set() should be used to add these addresses to the name resolver's output. The built-in "dns" name resolver already does this.
      resolver: add new field Endpoints to State and deprecate Addresses (resolver: State: add Endpoints and deprecate Addresses grpc/grpc-go#6471)
    • Addresses will be deleted in the future.
    • See NOTICE: Upcoming API changes to experimental Name Resolver (resolver) and LB Policy (balancer) packages grpc/grpc-go#6472 for more details about these changes

The changes introduced in 1.58.0 are addressed in this pull-request.

[jgraettinger]

LGTM