[Debug] [Coroutines] Add deref operator for non complex expression

Background:

When we construct coroutine frame, we would insert a dbg.declare
intrinsic for it:
```
%hdl = call void @llvm.coro.begin() ; would return coroutine handle
call void @llvm.dbg.declare(metadata ptr %hdl, metadata
![[DEBUG_VARIABLE: __coro_frame]], metadata !DIExpression())
```

And in the splitted coroutine, it looks like:
```
define void @coro_func.resume(ptr *hdl) {
entry.resume:
    call void @llvm.dbg.declare(metadata ptr %hdl, metadata
![[DEBUG_VARIABLE: __coro_frame]], metadata !DIExpression())
}
```

And we would salvage the debug info by inserting a new alloca here:
```
define void @coro_func.resume(ptr %hdl) {
entry.resume:
    %frame.debug = alloca ptr
    call void @llvm.dbg.declare(metadata ptr %frame.debug, metadata
![[DEBUG_VARIABLE: __coro_frame]], metadata !DIExpression())
    store ptr %hdl, %frame.debug
}
```

But now, the problem comes since the `dbg.declare` refers to the address
of that alloca instead of actual coroutine handle. I saw there are codes
to solve the problem but it only applies to complex expression only. I
feel if it is OK to relax the condition to make it work for
`__coro_frame`.

Reviewed By: jmorse

Differential Revision: https://reviews.llvm.org/D126277