rebase: bump google.golang.org/grpc from 1.62.1 to 1.63.2

Bumps [google.golang.org/grpc](https://github.com/grpc/grpc-go) from 1.62.1 to 1.63.2.
- [Release notes](https://github.com/grpc/grpc-go/releases)
- [Commits](https://github.com/grpc/grpc-go/compare/v1.62.1...v1.63.2)

---
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/service_config.go

@@ -25,8 +25,10 @@ import (
 	"reflect"
 	"time"
 
+	"google.golang.org/grpc/balancer"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/internal"
+	"google.golang.org/grpc/internal/balancer/gracefulswitch"
 	internalserviceconfig "google.golang.org/grpc/internal/serviceconfig"
 	"google.golang.org/grpc/serviceconfig"
 )
@@ -41,11 +43,6 @@ const maxInt = int(^uint(0) >> 1)
 // https://github.com/grpc/grpc/blob/master/doc/service_config.md
 type MethodConfig = internalserviceconfig.MethodConfig
 
-type lbConfig struct {
-	name string
-	cfg  serviceconfig.LoadBalancingConfig
-}
-
 // ServiceConfig is provided by the service provider and contains parameters for how
 // clients that connect to the service should behave.
 //
@@ -55,14 +52,9 @@ type lbConfig struct {
 type ServiceConfig struct {
 	serviceconfig.Config
 
-	// LB is the load balancer the service providers recommends.  This is
-	// deprecated; lbConfigs is preferred.  If lbConfig and LB are both present,
-	// lbConfig will be used.
-	LB *string
-
 	// lbConfig is the service config's load balancing configuration.  If
 	// lbConfig and LB are both present, lbConfig will be used.
-	lbConfig *lbConfig
+	lbConfig serviceconfig.LoadBalancingConfig
 
 	// Methods contains a map for the methods in this service.  If there is an
 	// exact match for a method (i.e. /service/method) in the map, use the
@@ -164,7 +156,7 @@ type jsonMC struct {
 // TODO(lyuxuan): delete this struct after cleaning up old service config implementation.
 type jsonSC struct {
 	LoadBalancingPolicy *string
-	LoadBalancingConfig *internalserviceconfig.BalancerConfig
+	LoadBalancingConfig *json.RawMessage
 	MethodConfig        *[]jsonMC
 	RetryThrottling     *retryThrottlingPolicy
 	HealthCheckConfig   *healthCheckConfig
@@ -184,18 +176,33 @@ func parseServiceConfig(js string) *serviceconfig.ParseResult {
 		return &serviceconfig.ParseResult{Err: err}
 	}
 	sc := ServiceConfig{
-		LB:                rsc.LoadBalancingPolicy,
 		Methods:           make(map[string]MethodConfig),
 		retryThrottling:   rsc.RetryThrottling,
 		healthCheckConfig: rsc.HealthCheckConfig,
 		rawJSONString:     js,
 	}
-	if c := rsc.LoadBalancingConfig; c != nil {
-		sc.lbConfig = &lbConfig{
-			name: c.Name,
-			cfg:  c.Config,
+	c := rsc.LoadBalancingConfig
+	if c == nil {
+		name := PickFirstBalancerName
+		if rsc.LoadBalancingPolicy != nil {
+			name = *rsc.LoadBalancingPolicy
 		}
+		if balancer.Get(name) == nil {
+			name = PickFirstBalancerName
+		}
+		cfg := []map[string]any{{name: struct{}{}}}
+		strCfg, err := json.Marshal(cfg)
+		if err != nil {
+			return &serviceconfig.ParseResult{Err: fmt.Errorf("unexpected error marshaling simple LB config: %w", err)}
+		}
+		r := json.RawMessage(strCfg)
+		c = &r
 	}
+	cfg, err := gracefulswitch.ParseConfig(*c)
+	if err != nil {
+		return &serviceconfig.ParseResult{Err: err}
+	}
+	sc.lbConfig = cfg
 
 	if rsc.MethodConfig == nil {
 		return &serviceconfig.ParseResult{Config: &sc}