rebase: bump google.golang.org/grpc from 1.55.0 to 1.56.0

Bumps [google.golang.org/grpc](https://github.com/grpc/grpc-go) from 1.55.0 to 1.56.0.
- [Release notes](https://github.com/grpc/grpc-go/releases)
- [Commits](https://github.com/grpc/grpc-go/compare/v1.55.0...v1.56.0)

---
updated-dependencies:
- dependency-name: google.golang.org/grpc
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

vendor/google.golang.org/grpc/picker_wrapper.go

@@ -36,6 +36,7 @@ import (
 type pickerWrapper struct {
 	mu         sync.Mutex
 	done       bool
+	idle       bool
 	blockingCh chan struct{}
 	picker     balancer.Picker
 }
@@ -47,7 +48,11 @@ func newPickerWrapper() *pickerWrapper {
 // updatePicker is called by UpdateBalancerState. It unblocks all blocked pick.
 func (pw *pickerWrapper) updatePicker(p balancer.Picker) {
 	pw.mu.Lock()
-	if pw.done {
+	if pw.done || pw.idle {
+		// There is a small window where a picker update from the LB policy can
+		// race with the channel going to idle mode. If the picker is idle here,
+		// it is because the channel asked it to do so, and therefore it is sage
+		// to ignore the update from the LB policy.
 		pw.mu.Unlock()
 		return
 	}
@@ -63,10 +68,8 @@ func (pw *pickerWrapper) updatePicker(p balancer.Picker) {
 //   - wraps the done function in the passed in result to increment the calls
 //     failed or calls succeeded channelz counter before invoking the actual
 //     done function.
-func doneChannelzWrapper(acw *acBalancerWrapper, result *balancer.PickResult) {
-	acw.mu.Lock()
-	ac := acw.ac
-	acw.mu.Unlock()
+func doneChannelzWrapper(acbw *acBalancerWrapper, result *balancer.PickResult) {
+	ac := acbw.ac
 	ac.incrCallsStarted()
 	done := result.Done
 	result.Done = func(b balancer.DoneInfo) {
@@ -152,14 +155,14 @@ func (pw *pickerWrapper) pick(ctx context.Context, failfast bool, info balancer.
 			return nil, balancer.PickResult{}, status.Error(codes.Unavailable, err.Error())
 		}
 
-		acw, ok := pickResult.SubConn.(*acBalancerWrapper)
+		acbw, ok := pickResult.SubConn.(*acBalancerWrapper)
 		if !ok {
 			logger.Errorf("subconn returned from pick is type %T, not *acBalancerWrapper", pickResult.SubConn)
 			continue
 		}
-		if t := acw.getAddrConn().getReadyTransport(); t != nil {
+		if t := acbw.ac.getReadyTransport(); t != nil {
 			if channelz.IsOn() {
-				doneChannelzWrapper(acw, &pickResult)
+				doneChannelzWrapper(acbw, &pickResult)
 				return t, pickResult, nil
 			}
 			return t, pickResult, nil
@@ -187,6 +190,25 @@ func (pw *pickerWrapper) close() {
 	close(pw.blockingCh)
 }
 
+func (pw *pickerWrapper) enterIdleMode() {
+	pw.mu.Lock()
+	defer pw.mu.Unlock()
+	if pw.done {
+		return
+	}
+	pw.idle = true
+}
+
+func (pw *pickerWrapper) exitIdleMode() {
+	pw.mu.Lock()
+	defer pw.mu.Unlock()
+	if pw.done {
+		return
+	}
+	pw.blockingCh = make(chan struct{})
+	pw.idle = false
+}
+
 // dropError is a wrapper error that indicates the LB policy wishes to drop the
 // RPC and not retry it.
 type dropError struct {