Use any TypeNode for Account data

[lorisleiva]

This is a proposal that needs further discussion before implementing.

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Currently, the data of an AccountNode must be a StructAccountNode meaning its top-level data-structure must include named fields.

Technically, since data is just data, we could imagine an AccountNode with a simple BooleanTypeNode as data.

The issue with this approach is some other nodes such as the FieldDiscriminatorNode points to a field on the account and therefore expects the data to be a struct with named fields.