perf improvements#75

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beltram wants to merge 3 commits intofeat/rfc9420from

Commits on Jan 8, 2024

perf: cut down one iteration over the tree in 'free_leaf_index'
beltram
committed
perf: remove needless node clone in 'TreeSync::from_ratchet_tree'
beltram
committed
perf: prevent unnecessary boxing in 'copath()' and use iterators
beltram
committed