[clang] Fix parenthesized list initialization of arrays not working with `new` (#76976)

This bug is caused by parenthesized list initialization not being
implemented in `CodeGenFunction::EmitNewArrayInitializer(...)`.

Parenthesized list initialization of `struct`s with `operator new`
already works in Clang and is not affected by this bug.

Additionally, fix the test new-delete.cpp as it incorrectly assumes that
using parentheses with operator new to initialize arrays is illegal for
C++ versions >= C++17.

Fixes #68198