[META] Claro theme UI improvements

Problem/Motivation

We want to improve the UI integration with the Claro theme. While testing other tickets, we found out a couple of issues that we will list here and fix in subtasks. This issue will serve as a meta issue with a general overview.

Things to fix (listed here: #3103995-6: Improve visual coherence in Claro in combination with Field group horizontal tabs):

• Broken buttons #3079128: Broken Dropdown prevents Save in Claro
• #3108875: Convert overflowing paragraph summary gradient to ellipsis
• #3112668: Drag & drop handles are misaligned on the left
• "to paragraph" text after the dropdown button is missing spaces (will be fixed with #3079128: Broken Dropdown prevents Save in Claro)
• #3104790: Dropdown button broken when toggling Behavior tab
• #3092181: Nested Paragraphs create multiple drag handles
• #3111070: Reduce whitespace in 'All paragraph' modal in Claro
• Generally big whitespaces and indentation
• #3111075: Use small button component for Claro
• #3181786: Missing Margin for Paragraph Buttons in Claro Theme
• #3199551: The content/behavior tabs on the paragraphs widget don't render properly in Claro.
• #3268122: Button "Add above" is missing with Gin theme enabled
• #3281151: Remove extra margin on 'add paragraph' button on claro
• #3332030: Wider Paragraphs content editing form widget

Most of the issues above were reported in this comment with screenshots: #3103995-6: Improve visual coherence in Claro in combination with Field group horizontal tabs

Related core issue:

• #3099026: Claro's preprocessing of field multiple value form's table header cell removes potential changes by others
• #3292488: Move button--small class for add more field widget button to WidgetBase