Auto merge of #86031 - ssomers:btree_lazy_iterator, r=Mark-Simulacrum

BTree: lazily locate leaves in rangeless iterators

BTree iterators always locate both the first and last leaf edge and often only need either one, i.e., whenever they are traversed in a single direction, like in for-loops and in the common use of `iter().next()` or `iter().next_back()` to retrieve the first or last key/value-pair (#62924). It's fairly easy to avoid because the iterators with this disadvantage already are quite separate from other iterators.

r? `@Mark-Simulacrum`

0 files changed, 0 insertions, 0 deletions