refactor: deduplicate utility helpers across the codebase (#23338)

Audited exported helpers in `coderd/util/*`, `testutil`, `cryptorand`,
and friends, then replaced duplicated implementations with canonical
versions.

- **fix: `maps.SortedKeys` generic signature** — value type was
hardcoded to `any`, making it impossible to actually call. Added second
type parameter `V any`. Added table-driven tests with `cmp.Diff`.
- **refactor: replace ad-hoc ptr helpers with `ptr.Ref`** — removed
`int64Ptr`, `stringPtr`, `boolPtr`, `i64ptr`, `strPtr`, `PtrInt32`
across 6 files.
- **refactor: replace local `sortedKeys`/`sortKeys` with
`maps.SortedKeys`** — now that the signature is fixed, scripts can use
it.
- **refactor: replace hand-rolled `capitalize` with
`strings.Capitalize`** — the typegen version was also not UTF-8 safe.

> 🤖 This PR was created with the help of Coder Agents, and was reviewed
by my human. 🧑‍💻

scripts/typegen/main.go

@@ -20,6 +20,7 @@ import (
 
 	"github.com/coder/coder/v2/coderd/rbac"
 	"github.com/coder/coder/v2/coderd/rbac/policy"
+	utilstrings "github.com/coder/coder/v2/coderd/util/strings"
 	"github.com/coder/coder/v2/codersdk"
 )
 
@@ -131,15 +132,11 @@ func generateCountries() ([]byte, error) {
 func pascalCaseName[T ~string](name T) string {
 	names := strings.Split(string(name), "_")
 	for i := range names {
-		names[i] = capitalize(names[i])
+		names[i] = utilstrings.Capitalize(names[i])
 	}
 	return strings.Join(names, "")
 }
 
-func capitalize(name string) string {
-	return strings.ToUpper(string(name[0])) + name[1:]
-}
-
 type Definition struct {
 	policy.PermissionDefinition
 	Type string
@@ -226,7 +223,7 @@ func generateRbacObjects(templateSource string) ([]byte, error) {
 	var errorList []error
 	var x int
 	tpl, err := template.New("object.gotmpl").Funcs(template.FuncMap{
-		"capitalize":     capitalize,
+		"capitalize":     utilstrings.Capitalize,
 		"pascalCaseName": pascalCaseName[string],
 		"actionsList": func() []ActionDetails {
 			return actionList