Restore numeric from String constructors

[KoBeWi]

Closes #44407

[akien-mga]

Lots of CI build errors along those lines:

core/variant/variant_construct.h: In static member function 'static void VariantConstructorFromString<T>::ptr_construct(void*, const void**) [with T = long int]':
core/variant/variant_construct.h:258:11: error: 'dst_var' may be used uninitialized in this function [-Werror=maybe-uninitialized]
  258 |   Variant type_test = Variant(dst_var);
      |           ^~~~~~~~~
core/variant/variant_construct.h: In static member function 'static void VariantConstructorFromString<T>::ptr_construct(void*, const void**) [with T = double]':
core/variant/variant_construct.h:258:11: error: 'dst_var' may be used uninitialized in this function [-Werror=maybe-uninitialized]
  258 |   Variant type_test = Variant(dst_var);
      |           ^~~~~~~~~

[cdemirer]

I guess GetTypeInfo<T>::VARIANT_TYPE can be used instead of dummy Variants.

[reduz]

I am not happy with this kind of automatic cast, as it an be quite prone to errors. We discussed with @vnen at that point in time and believed it would be better you use the str() function instead in GDScript.

[KoBeWi]

But the PR is about int("string"). It no longer works in 4.0. I don't know how it works internally; if it causes implicit conversions then I agree it's bad :/

[KoBeWi]

I checked and this

var a: int
a = "123"

does not work, so I guess it's fine? 🤔

[Mickeon]

To me this looks completely fine. Reduz may have gotten confused. I tried myself, and no implicit conversion is done. There may be other circumstances where it is, however?

[akien-mga]

Thanks!