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/delete_helmrelease.go

@@ -29,6 +29,7 @@ var deleteHelmReleaseCmd = &cobra.Command{
 	Long:    "The delete helmrelease command removes the given HelmRelease from the cluster.",
 	Example: `  # Delete a Helm release and the Kubernetes resources created by it
   flux delete hr podinfo`,
+	ValidArgsFunction: resourceNamesCompletionFunc(helmv2.GroupVersion.WithKind(helmv2.HelmReleaseKind)),
 	RunE: deleteCommand{
 		apiType: helmReleaseType,
 		object:  universalAdapter{&helmv2.HelmRelease{}},