Simplify TransactionKernel package APIs

#3146 added package debug execution, so `TransactionKernel` now exposes package, program, debug info, and entrypoint source node separately.

Motivating PR comment:

- https://github.com/0xMiden/protocol/pull/3146#discussion_r3516257274

The main path is [`crates/miden-protocol/src/transaction/kernel/mod.rs`](https://github.com/0xMiden/protocol/blob/2432a082e53c7e16b2885c8ee42e05489480358c/crates/miden-protocol/src/transaction/kernel/mod.rs#L73-L163). The package debug accessors are new in #3146, so this permalink points at the PR head.

Callers now combine these separate values in:

- [`crates/miden-tx/src/executor/mod.rs`](https://github.com/0xMiden/protocol/blob/2432a082e53c7e16b2885c8ee42e05489480358c/crates/miden-tx/src/executor/mod.rs#L202-L266)
- [`crates/miden-tx/src/executor/notes_checker.rs`](https://github.com/0xMiden/protocol/blob/2432a082e53c7e16b2885c8ee42e05489480358c/crates/miden-tx/src/executor/notes_checker.rs#L439-L449)

Please reshape `TransactionKernel` around package first access after the VM package execution API exists.

The kernel should expose the few values callers need, without making each caller know how to pair a program with package debug info and an entrypoint source node.