completion: add completion for swarm "--filter" flags

[JessThrysoee]

The migration to the generated (V2) shell completions dropped the "--filter" key/value suggestions that the legacy bash completion used to provide for the swarm commands, so e.g. "docker service ps --filter " no longer completed anything.

Register filter completions for "docker service ps", "docker service ls", and "docker node ps", following the same approach as the existing completion for "docker events --filter".

[codecov-commenter]

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✅ All modified and coverable lines are covered by tests.

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[thaJeztah]

I'm guessing the old bash-completion couldn't easily do this because the CLI does not have a comment to list tasks, but as a follow up we could look if we actually could use the API client for this;

cli/cli/command/node/ps.go

Lines 75 to 82 in 4f7c07c

	filter := options.filter.Value()
	filter.Add("node", res.Node.ID)
	nodeTasks, err := apiClient.TaskList(ctx, client.TaskListOptions{Filters: filter})
	if err != nil {
	errs = append(errs, err)
	continue
	}

Definitely OK for a follow-up though, no need to cramp it into this PR.

[JessThrysoee]

• label= a TaskList/ServiceList call and pluck the label from the Items
• name= a little heavier with multiple api calls, should system.taskNames be made available for this?
• id= probably not as useful, but also just a TaskList call

But I think you are right, this feels like a separate PR.

[thaJeztah]

Yup! No need to do it for this one; I was only glancing over the changes (at a glance they look great! but will have a closer look tomorrow), and was thinking out loud to see if we could fill in the remaining bits.

But indeed; more than fine for a follow-up, so that we can see if it makes sense (outweigh the overhead against how much it improves).

[thaJeztah]

(marked it "unresolved" so that it stays visible, but no need to fix)