lang: Add `space` attribute to the InitSpace macro

[Aursen]

Problem

#2765

Summary of changes

• Add attribute space to InitSpace macro

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[Aursen]

Thanks. What happens when the space is not enough?

#[space(2)]
pub data: Vec<u64>,

It will not check if the length is valid. This attribute is designed to give the user freedom

[acheroncrypto]

Freedom to run into a guaranteed error in runtime? It feels like we have enough information to make this a compile error — what do you think?

[Aursen]

Freedom to run into a guaranteed error in runtime? It feels like we have enough information to make this a compile error — what do you think?

The only issue with this, when a user uses const or other thing like this for the value of space we can't verify the space

[acheroncrypto]

Yeah, I don't think it needs to be perfect, just the easy parts we can easily handle. It's also not required to merge this, but it would be an improvement over the current impl.