Deepen package procedure access APIs

0xMiden/protocol#3146 exposed a gap between miden-vm package APIs and protocol account code.

Motivating PR comments:

• https://github.com/0xMiden/protocol/pull/3146#discussion_r3516208770
• https://github.com/0xMiden/protocol/pull/3146#discussion_r3516217416
• https://github.com/0xMiden/protocol/pull/3146#discussion_r3516223720

Package::get_procedure_root_by_path and Package::get_procedure_node_by_path already cover direct path lookup in crates/mast-package/src/package/mod.rs. That is enough for one protocol method.

Protocol still has to read package internals for account interface procedures:

• crates/miden-protocol/src/account/component/code.rs reads package exports and filters ProcedureExport attributes.
• crates/miden-protocol/src/account/component/mod.rs reads the export node to compute account procedure roots.

The existing direct lookup API is in crates/mast-package/src/package/mod.rs.

Please add package APIs that hide that shape:

• iterate procedure exports by attribute.
• return the resolved procedure root for an export, using the export node when present.
• avoid direct downstream reads of Package::manifest, ProcedureExport::node, and Package::mast_forest() for this common case.

After that, protocol account code can ask the package for interface procedure roots instead of rebuilding that logic.