Implemented the NestedCategoryFilterWidget

[fkloes]

Description

This ticket is about to implement the nested category filter widget for iOS and GMD.
It also improves the "selected" state visualization of option and characteristic pickers on the PDP.

Type of change

• Bug Fix 🐛 (non-breaking change which fixes an issue)
• New Feature 🚀 (non-breaking change which adds functionality)
• Breaking Change 💥 (fix or feature that would cause existing functionality to not work as expected)
• Polish 💅 (Just some cleanups)
• Docs 📝 (Changes in the documentations)
• Internal 🏠 Only relates to internal processes.

[coveralls]

Pull Request Test Coverage Report for Build 1989

• 45 of 48 (93.75%) changed or added relevant lines in 12 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.4%) to 47.255%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
themes/theme-ios11/pages/Product/components/Characteristics/Characteristic/components/SheetItem/style.js	0	3	0.0%

Totals
Change from base Build 1988:	0.4%
Covered Lines:	5041
Relevant Lines:	10004

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💛 - Coveralls