Extract user-facing types into `miden-objects` crate (unified Miden SDK types)

[greenhat]

Relevant issue in the compiler repo: 0xMiden/compiler#870.

Why

1. To pass the user-defined types containing Miden SDK types (Asset, AccountId, etc.) between the on-chain and off-chain code. For example, a note struct deserialized from the note storage can contain an AccountId value. Using the schema defined in the on-chain code (note), we will generate the off-chain type for the note. We want to reference the same AccountId type that is used in the on-chain (note) note type definition.
2. Unify the API (helper methods) between the on-chain and off-chain user code.

What

Any type that is used in the tx kernel MASM procedures that have Rust bindings in the Miden on-chain SDK.

The list of types:

• Asset
• AccountId
• Recipient (Digest only)
• NoteMetadata
• NoteTag
• NoteType

How

We need to define these types in the separate crate (miden-objects) which will be a dependency to the Miden SDK crates in the compiler repo. The separate crate is needed to avoid pulling the whole miden-protocol into the Miden SDK.

In the Miden SDK API, we will re-export these types and use them in the Miden SDK API (functions).

/cc @bobbinth @bitwalker

[mmagician]

The separate crate is needed to avoid pulling the whole miden-protocol into the Miden SDK.

Is this to reduce the size of the pulled-in dependencies?

We've had some refactorings in the past to move in the opposite direction (we used to have miden-objects, it was refactored in favor of miden-protocol as part of #2197 and #2191)

[bobbinth]

The idea here is that we'd have miden-objects that define "protocol level objects" but not the protocol functionality itself. In this way, the dependency would be:

miden-objects -> miden-protocol -> miden-standards

For example, the AccountId struct would live in miden-objects. This would include basic accessors and serialization logic, but the business logic of using account IDs would live in miden-protocol.

At least this is the intent, not sure how well it'll actually work in practice.