[C++20][Coroutines] Lambda-coroutine with operator new in promise_type (#84193)

Fix #84064

According to http://eel.is/c++draft/dcl.fct.def.coroutine#9 the first
parameter for overload resolution of `operator new` is `size_t` followed
by the arguments of the coroutine function.
http://eel.is/c++draft/dcl.fct.def.coroutine#4 states that the first
argument is the lvalue of `*this` if the coroutine is a member function.

Before this patch, Clang handled class types correctly but ignored
lambdas. This patch adds support for lambda coroutines with a
`promise_type` that implements a custom `operator new`.

The patch does consider C++23 `static operator()`, which already worked
as there is no `this` parameter.