Issue #3311455: Support field_groups nesting

added 26 commits

• f45c72d0...980d8ba1 - 24 commits from branch project:8.x-1.x
• 10db4089 - Issue #3311455: Child have parent settings.
• 68f3954d - Merge branch '8.x-1.x' into 3311455-support-fieldgroups-nesting

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