[lldb] Support MS style `struct`/`class` in C++ name parser (#196525)
If a type is declared as a `class` or a `struct` is part of the mangled
name in the Microsoft ABI. This is also reflected in the demangled name.
There, it shows up before the qualified name. For example, you could
have `class ns1::ns2::MyClass`. It will show up like this in return
types and function/template arguments.
This adds a check in `CPlusPlusNameParser::ParseFullNameImpl` for these
cases.