[clang] Fix CTAD not work for C++ explicit type conversion (functional annotation). (#75779)

This fixes https://github.com/llvm/llvm-project/issues/64347.

The CTAD for an aggregate class is missing to handle the explicit type
conversion case, e.g. `TemplateFooClass(1, 2);`. Per C++ expr.type.conv
p1, the deduced type is the return type of the deduction guide selected
by the CTAD for the reminder.

In the deduction implementation
`DeduceTemplateSpecializationFromInitializer`, the parenthesized
express-list case relies on the `ParenListExpr` parameter (default is
nullptr), the AST `ParenListExpr` node is not built for all variant
initializer cases (`BuildCXXTypeConstructorExpr`, `BuildCXXNew` etc),
thus the deduction doesn't perform for these cases. This patch fixes it
by removing the `ParenListExpr` and using the `Inits` instead (which
also simplifies the interface and implementation).