feat: cli: consolidate schedule-related commands (#2402)

* feat: cli: consolidate schedule-related commands

This commit makes the following changes:
- renames autostart -> schedule starat
- renames ttl -> schedule stop
- renames bump -> schedule override
- adds schedule show command
- moves some cli-related stuff to util.go

coderd/util/ptr/ptr.go

@@ -17,6 +17,14 @@ func NilOrEmpty(s *string) bool {
 	return s == nil || *s == ""
 }
 
+// NilToEmpty coalesces a nil str to the empty string.
+func NilToEmpty(s *string) string {
+	if s == nil {
+		return ""
+	}
+	return *s
+}
+
 // NilOrZero returns true if v is nil or 0.
 func NilOrZero[T number](v *T) bool {
 	return v == nil || *v == 0