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/metricsdocgen/main.go

@@ -14,6 +14,7 @@ import (
 	"github.com/prometheus/common/expfmt"
 	"golang.org/x/xerrors"
 
+	"github.com/coder/coder/v2/coderd/util/maps"
 	"github.com/coder/coder/v2/scripts/atomicwrite"
 )
 
@@ -176,7 +177,7 @@ func updatePrometheusDoc(doc []byte, metricFamilies []*dto.MetricFamily) ([]byte
 		}
 
 		if len(labels) > 0 {
-			_, _ = buffer.WriteString(strings.Join(sortedKeys(labels), " "))
+			_, _ = buffer.WriteString(strings.Join(maps.SortedKeys(labels), " "))
 		}
 
 		_, _ = buffer.WriteString(" |\n")
@@ -190,12 +191,3 @@ func updatePrometheusDoc(doc []byte, metricFamilies []*dto.MetricFamily) ([]byte
 func writePrometheusDoc(doc []byte) error {
 	return atomicwrite.File(prometheusDocFile, doc)
 }
-
-func sortedKeys(m map[string]struct{}) []string {
-	var keys []string
-	for k := range m {
-		keys = append(keys, k)
-	}
-	sort.Strings(keys)
-	return keys
-}