Introduce SimpleSmt::with_contiguous_leaves()

[plafer]

Introduces SimpleSmt::with_contiguous_leaves() which is useful to build a SimpleSmt from complex iterator expressions, and where we want to pack all the leaves from index 0 and on.

For example, this is now possible (a pattern needed in miden-node to build the created notes tree):

// simplified
SimpleSmt::with_contiguous_leaves(
    DEPTH,
    note_envelopes
        .flat_map(|note| [note.note_hash(), note.metadata()])
        .collect::<Vec<_>>(),
)
.unwrap();

[sonarqubecloud]

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[hackaugusto]

lgtm