fix: replace moby/moby namesgenerator with internal implementation (#21377)

Replace the external moby/moby/pkg/namesgenerator dependency with an
internal implementation using gofakeit/v7. The moby package has ~25k
unique name combinations, and with its retry parameter only adds a
random digit 0-9, giving ~250k possibilities. In parallel tests, this
has led to collisions (flakes).

The new internal API at coderd/util/namesgenerator eliminates the
external dependnecy and offers functions with explicit uniqueness
guarantees. This PR also consolidates fragmented name generation in a
few places to use the new package.

| Old (moby/moby)                     | New                    |
|-------------------------------------|------------------------|
| namesgenerator.GetRandomName(0)     | NameWith("_")          |
| namesgenerator.GetRandomName(>0)    | NameDigitWith("_")     |
| testutil.GetRandomName(t)           | UniqueName()           |
| testutil.GetRandomNameHyphenated(t) | UniqueNameWith("-")    |

namesgenerator package API:
- NameWith(delim): random name, not unique
- NameDigitWith(delim): random name with 1-9 suffix, not unique
- UniqueName(): guaranteed unique via atomic counter
- UniqueNameWith(delim): unique with custom delimiter

Names continue to be docker style `[adjective][delim][surname]`. Unique
names are truncated to 32 characters (preserving the numeric suffix) to
fit common name length limits in Coder.

Related test flakes:
https://github.com/coder/internal/issues/1212
https://github.com/coder/internal/issues/118
https://github.com/coder/internal/issues/1068

enterprise/coderd/coderd_test.go

@@ -18,7 +18,6 @@ import (
 	"time"
 
 	"github.com/google/uuid"
-	"github.com/moby/moby/pkg/namesgenerator"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"go.uber.org/goleak"
@@ -42,6 +41,7 @@ import (
 	agplprebuilds "github.com/coder/coder/v2/coderd/prebuilds"
 	"github.com/coder/coder/v2/coderd/rbac"
 	"github.com/coder/coder/v2/coderd/rbac/policy"
+	"github.com/coder/coder/v2/coderd/util/namesgenerator"
 	"github.com/coder/coder/v2/coderd/util/ptr"
 	"github.com/coder/coder/v2/codersdk"
 	"github.com/coder/coder/v2/codersdk/workspacesdk"
@@ -1106,7 +1106,7 @@ func tcpEchoServer(t *testing.T) string {
 
 // nolint:revive // t takes precedence.
 func writeReadEcho(t *testing.T, ctx context.Context, conn net.Conn) {
-	msg := namesgenerator.GetRandomName(0)
+	msg := namesgenerator.UniqueName()
 
 	deadline, ok := ctx.Deadline()
 	if ok {