storage: gRPC client does not respect no proxy option

## Client

Storage

## Environment

Ubuntu noble x86 on GCP

go version go1.24.4 linux/amd64

## Code and Dependencies

```go
package main

import (
"context"
"errors"
"flag"
"log"
"os"

"cloud.google.com/go/storage"
"google.golang.org/api/option"
"google.golang.org/grpc"
)

func main() {
bucket := flag.String("bucket", "", "Bucket to use")

flag.Parse()

if *bucket == "" {
flag.Usage()
os.Exit(1)
}

ctx := context.Background()

client, err := storage.NewGRPCClient(
ctx,
option.WithGRPCDialOption(grpc.WithNoProxy()),
)
if err != nil {
log.Fatal(err)
}

_, err = client.Bucket(*bucket).Attrs(ctx)
if err != nil {
if errors.Is(err, storage.ErrBucketNotExist) {
log.Println("bucket does not exist")
return
}
log.Fatal(err)
}

log.Println("bucket exists")
}

```

go.mod

```text
module github.com/horgh/gcs-grpc-test

go 1.24.4

require (
cloud.google.com/go/storage v1.55.0
google.golang.org/api v0.236.0
google.golang.org/grpc v1.73.0
)

require (
cel.dev/expr v0.23.0 // indirect
cloud.google.com/go v0.121.1 // indirect
cloud.google.com/go/auth v0.16.1 // indirect
cloud.google.com/go/auth/oauth2adapt v0.2.8 // indirect
cloud.google.com/go/compute/metadata v0.7.0 // indirect
cloud.google.com/go/iam v1.5.2 // indirect
cloud.google.com/go/monitoring v1.24.2 // indirect
github.com/GoogleCloudPlatform/opentelemetry-operations-go/detectors/gcp v1.27.0 // indirect
github.com/GoogleCloudPlatform/opentelemetry-operations-go/exporter/metric v0.51.0 // indirect
github.com/GoogleCloudPlatform/opentelemetry-operations-go/internal/resourcemapping v0.51.0 // indirect
github.com/cespare/xxhash/v2 v2.3.0 // indirect
github.com/cncf/xds/go v0.0.0-20250326154945-ae57f3c0d45f // indirect
github.com/envoyproxy/go-control-plane/envoy v1.32.4 // indirect
github.com/envoyproxy/protoc-gen-validate v1.2.1 // indirect
github.com/felixge/httpsnoop v1.0.4 // indirect
github.com/go-jose/go-jose/v4 v4.0.5 // indirect
github.com/go-logr/logr v1.4.2 // indirect
github.com/go-logr/stdr v1.2.2 // indirect
github.com/google/s2a-go v0.1.9 // indirect
github.com/google/uuid v1.6.0 // indirect
github.com/googleapis/enterprise-certificate-proxy v0.3.6 // indirect
github.com/googleapis/gax-go/v2 v2.14.2 // indirect
github.com/planetscale/vtprotobuf v0.6.1-0.20240319094008-0393e58bdf10 // indirect
github.com/spiffe/go-spiffe/v2 v2.5.0 // indirect
github.com/zeebo/errs v1.4.0 // indirect
go.opentelemetry.io/auto/sdk v1.1.0 // indirect
go.opentelemetry.io/contrib/detectors/gcp v1.36.0 // indirect
go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.60.0 // indirect
go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.60.0 // indirect
go.opentelemetry.io/otel v1.36.0 // indirect
go.opentelemetry.io/otel/metric v1.36.0 // indirect
go.opentelemetry.io/otel/sdk v1.36.0 // indirect
go.opentelemetry.io/otel/sdk/metric v1.36.0 // indirect
go.opentelemetry.io/otel/trace v1.36.0 // indirect
golang.org/x/crypto v0.38.0 // indirect
golang.org/x/net v0.40.0 // indirect
golang.org/x/oauth2 v0.30.0 // indirect
golang.org/x/sync v0.14.0 // indirect
golang.org/x/sys v0.33.0 // indirect
golang.org/x/text v0.25.0 // indirect
golang.org/x/time v0.11.0 // indirect
google.golang.org/genproto v0.0.0-20250505200425-f936aa4a68b2 // indirect
google.golang.org/genproto/googleapis/api v0.0.0-20250512202823-5a2f75b736a9 // indirect
google.golang.org/genproto/googleapis/rpc v0.0.0-20250528174236-200df99c418a // indirect
google.golang.org/protobuf v1.36.6 // indirect
)
```

## Expected behavior

No proxy is used and GCS can be used

## Actual behavior

Proxy set in the `https_proxy` environment variable is used. I see connection attempts to `monitoring.googleapis.com` and `directpath-pa.googleapis.com`. Since my proxy doesn't allow connections to these, my program hangs trying to connect to them.

## Additional context

I've been using `cloud.google.com/go/storage` for some time and noticed there was gRPC support, so I wanted to switch to that.

My environment has an HTTP proxy set via environment variables, e.g. `export https_proxy=http://127.0.0.1:8888`.

For GCP APIs I don't want to use the proxy, so I disable using it via `option.WithGRPCDialOption(grpc.WithNoProxy())`. This doesn't seem to work for the GCS gRPC client right now.

If I leave it running for a while, I eventually see connection errors:

```
$ (cd go/foo/ && go run . -bucket foo)
2025/06/09 22:07:31 rpc error: code = Unavailable desc = connection error: desc = "transport: Error while dialing: dial tcp 127.0.0.1:8888: connect: connection refused"
```