feat(comp): Move to Cobra's bash completion V2

Cobra's bash completion V2 has the following benefits:
- aligned with the completion logic for the other shells
- provides completion descriptions as for the other shells
- uses a 300-line shell script (versus 4K lines for V1)

Signed-off-by: Marc Khouzam <marc.khouzam@montreal.ca>

cmd/helm/completion.go

@@ -102,12 +102,12 @@ func newCompletionCmd(out io.Writer) *cobra.Command {
 		Short:             "generate autocompletion script for bash",
 		Long:              bashCompDesc,
 		Args:              require.NoArgs,
-		DisableFlagsInUseLine: true,
 		ValidArgsFunction: noCompletions,
 		RunE: func(cmd *cobra.Command, args []string) error {
 			return runCompletionBash(out, cmd)
 		},
 	}
+	bash.Flags().BoolVar(&disableCompDescriptions, noDescFlagName, false, noDescFlagText)
 
 	zsh := &cobra.Command{
 		Use:               "zsh",
@@ -151,7 +151,7 @@ func newCompletionCmd(out io.Writer) *cobra.Command {
 }
 
 func runCompletionBash(out io.Writer, cmd *cobra.Command) error {
-	err := cmd.Root().GenBashCompletion(out)
+	err := cmd.Root().GenBashCompletionV2(out, !disableCompDescriptions)
 
 	// In case the user renamed the helm binary (e.g., to be able to run
 	// both helm2 and helm3), we hook the new binary name to the completion function