Hide the "numpy" module unless `--with-intrinsic-mods` is used

The ASR shows:
```
 numpy:
 (Module
 (SymbolTable
 3
 {
 __lpython_overloaded_0__arccos:
 (Function
 (SymbolTable
 41
 {
 _lpython_return_variable:
```
But this should be hidden unless `--with-intrinsic-mods` is used.