Replace deprecated slot setters

What does this MR do and why?

This updates all remaining deprecated ViewComponent slot setter usages in our codebase.

The old way (c.SLOT_NAME) got deprecated in the later 2.x versions of the view_component gem and now got completely removed in the recent 3.0 release. We have to replace all deprecated calls before we can Upgrade to view_component v3.0 (#408988 - closed).

Because we had hundreds of lines in ~200 files to update, I do it in batches to get smaller, more reviewable MRs. This is one of them. The last one actually... hopefully :) See the checklist in #408988 (closed) for the already merged MRs.

Screenshots or screen recordings

No visual changes.

How to set up and validate locally

• We are currently on the latest 2.x version of the view_component gem. Both ways to set the slot work here, so there shouldn't be any functional changes, but feel free to browse around in the affected areas of the UI for a few samples.
• Focus on the diff itself. Check that I made no search&replace mistakes there. Thanks!

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

spec/components/previews/pajamas/checkbox_tag_component_preview.rb

-# frozen_string_literal: true
-
-module Pajamas
-  class CheckboxTagComponentPreview < ViewComponent::Preview
-    # @param name text
-    # @param checked toggle
-    # @param value text
-    def default(name: "my-checkbox-tag", checked: true, value: '1')
-      render(Pajamas::CheckboxTagComponent.new(
-        name: name,
-        checked: checked,
-        value: value
-      )) do |c|
-        c.with_label do
-          "Label text is a #{content_tag(:em, 'slot')}.".html_safe
-        end
-        c.with_help_text do
-          "The help text is a slot, too."
-        end
-      end
-    end
-  end
-end