Early processing of deltas related to network accounts

> Not for this PR, but somewhere (probably much further upstream), we should try to detect if the delta is trying to introduce (or update) the storage slot that identifies network accounts. In case such a storage slot is being added to an existing account, we should throw an error (accounts cannot become network accounts after creation), if it is an update, then NTX builder will need to update the set of notes that the account is able to process.

_Originally posted by @bobbinth in https://github.com/0xMiden/node/pull/2132#discussion_r3307506060_

Pretty self explanatory, but the idea is to error early when an account is trying to become a network account, and also propagate any changes related to a network account metadata.