feat(standards): P2ID/P2IDE notes must carry at least one asset

[VAIBHAVJINDAL3012]

This PR add the assertion check for the case that there should be atleast one asset in the note when add_assets_to_account function is called.

[BREAKING] Enforced at both layers:

• Rust: P2idNote::create / P2ideNote::create return the new NoteError::MissingAsset on empty assets.
• MASM: basic_wallet::add_assets_to_account asserts num_assets > 0 (new ERR_BASIC_WALLET_EMPTY_NOTE_ASSETS).

closes #2978

[bobbinth]

Question (without having looked at the code): do we want to do anything about a fungible asset with 0 amount? Technically, it is an asset, but conceptually, it is the same as no assets.

[VAIBHAVJINDAL3012]

Question (without having looked at the code): do we want to do anything about a fungible asset with 0 amount? Technically, it is an asset, but conceptually, it is the same as no assets.

Technically we shouldn't allow it but it still doesn't have any attack vector. We can also put checks while transferring asset to account that asset value shouldn't be 0.

[bobbinth]

We can also put checks while transferring asset to account that asset value shouldn't be 0.

This may be tricky as we can't check this for all assets in general (especially, at the protocol level) - e.g., "custom" assets would be excluded.

[VAIBHAVJINDAL3012]

This may be tricky as we can't check this for all assets in general (especially, at the protocol level) - e.g., "custom" assets would be excluded.

Which assets have value 0?

[bobbinth]

This may be tricky as we can't check this for all assets in general (especially, at the protocol level) - e.g., "custom" assets would be excluded.

Which assets have value 0?

Fungible assets currently. In the future, we'll have "custom" asset with asset-specific structure - so, inferring whether an asset is a "zero" asset by looking at the asset itself, may not be possible in generality.

But we may be able to do the check in a different way: if the root of the asset vault didn't change after the asset was added, we know that adding an asset didn't have an effect. I haven't looked into the code to know how easy/viable it is to perform this check - but it may be not too bad.