Invalid `From<&VariantArray> for Packed*Array` impls

[Bromeon]

There are lots of From implementations from VariantArray to Packed*Array:

impl From<&Array<Variant>> for PackedByteArray {...}
impl From<&Array<Variant>> for PackedColorArray {...}
...

This is of course incorrect, as the variants may hold different types and From must be infallible.
They are implemented here:

gdext/godot-core/src/builtin/collections/packed_array.rs

Line 604 in f67a1ae

impl_builtin_froms!($PackedArray; VariantArray => $from_array);

gdext/godot-core/src/builtin/macros.rs

Lines 126 to 142 in f67a1ae

	macro_rules! impl_builtin_froms {
	($To:ty; $($From:ty => $from_fn:ident),* $(,)?) => {
	$(impl From<&$From> for $To {
	fn from(other: &$From) -> Self {
	unsafe {
	// TODO should this be from_sys_init_default()?
	Self::new_with_uninit(|ptr| {
	let args = [other.sys()];
	::godot_ffi::builtin_call! {
	$from_fn(ptr, args.as_ptr())
	}
	})
	}
	}
	})*
	};
	}

Instead, we should use TryFrom or a named conversion method. Also, we could add infallible conversions from concretely typed arrays, e.g. Array<Color> <-> PackedColorArray in both directions. Right now, there is only PackedColorArray -> VariantArray.

Overall, From/TryFrom is probably OK here, but named methods are a potential alternative. We need to keep in mind that there are other conversions, e.g. between slices, Vec and so on, so maybe enabling generic programming is beneficial here.