Address advice witness redundancy

The `TransactionWitness` struct currently [contains some redundancy](https://github.com/0xPolygonMiden/miden-base/blob/96c28ef43ef1c4b92baefa3f6ea91600a021b2fe/crates/miden-objects/src/transaction/tx_witness.rs#L21-L24) which should be minimized.

In order to do so, @bobbinth suggests the following:

> - All advice-related data could go into the advice_witness field. This could include everything that would be needed for executing the transaction including things like TransactionArgs.advice_inputs, note args, some data from the foreign account inputs etc.
> - All code-related data could go into a single field which could be a vector of MastForests (or maybe even a single merged MAST forest).
>
>Basically, `TransactionWitness` would contain some metadata about the transaction, but the data that needs to be go into the advice provider and MAST forest store would be stored separately.

[(Reference comment)](https://github.com/0xPolygonMiden/miden-base/pull/1229#discussion_r2041239982)