Add Rename test cases for C++17 features

[LegalizeAdulthood]

Rename identifiers in

• fold expressions
• constexpr if
• structured bindings
  • assignment statement
  • structured binding range declaration
• initializers in if statements
• initializers in switch statements
• inline variables
• Templates:
  • typename template template parameters
  • placeholder template parameters
  • deduced class template parameters
  • template non-type arguments
• u8 character literals
• using declaration with multiple declarators
• pack expansions in using declarations