Add dynamic completion suppport

This commit adds dynamic completion support for the following commands
and flags:

- `flux delete ...` command
- `flux export ...` command
- `flux get ...` command
- `flux reconcile ...` command
- `flux resume ...` command
- `flux suspend ...` command
- `--namespace` flag
- `--context` flag

Signed-off-by: Kazuki Suda <kazuki.suda@gmail.com>

cmd/flux/suspend_image_updateauto.go

@@ -28,6 +28,7 @@ var suspendImageUpdateCmd = &cobra.Command{
 	Long:  "The suspend image update command disables the reconciliation of a ImageUpdateAutomation resource.",
 	Example: `  # Suspend reconciliation for an existing ImageUpdateAutomation
   flux suspend image update latest-images`,
+	ValidArgsFunction: resourceNamesCompletionFunc(autov1.GroupVersion.WithKind(autov1.ImageUpdateAutomationKind)),
 	RunE: suspendCommand{
 		apiType: imageUpdateAutomationType,
 		object:  imageUpdateAutomationAdapter{&autov1.ImageUpdateAutomation{}},