[C++20] [Modules] Fix the duplicated static initializer problem (#114193)

Reproducer:

```
//--- a.cppm
export module a;
int func();
static int a = func();

//--- a.cpp
import a;
```

Th

[C++20] [Modules] Fix the duplicated static initializer problem (#114193)

Reproducer:

```
//--- a.cppm
export module a;
int func();
static int a = func();

//--- a.cpp
import a;
```

The `func()` should only execute once. However, before this patch we
will somehow import `static int a` from a.cppm incorrectly and
initialize that again.

This is super bad and can introduce serious runtime behaviors.

And also surprisingly, it looks like the root cause of the problem is
simply some oversight choosing APIs.

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