fixes#24998
Basically it retraces back to the situation before
https://github.com/nim-lang/Nim/pull/18366 and
https://github.com/nim-lang/Nim/pull/18362, i.e.
```nim
import fuzz/a
import fuzz/a
```
```nim
import fuzz/a
from buzz/a
```
```nim
import fuzz/a except nil
from fuzz/a import addInt
```
All of these cases are now flagged as invalid and triggers a
redefinition error, i.e., each module name importing is treated as
consistent as the symbol definition
kinda annoying for importing/exporting with `when conditions` though
ref https://github.com/nim-lang/Nim/issues/18762https://github.com/nim-lang/Nim/issues/20907
```nim
from std/strutils import toLower
when not defined(js):
from std/strutils import toUpper
```
87ee9c84cb