perf: add batch write of BTreeMap node children addresses (#365)

This PR introduces batch writing of BTreeMap node children addresses to
improve performance.

This PR follows the idea from
#364 to batch
individual writes.
Although there are no significant changes overall, the majority of cases
show slight improvements (p25–p75: approx -0.07%), with: worst +0.27%,
median 0.00%, best -1.28%.

btreemap
```
  instructions:
    status:   No significant changes 👍
    counts:   [total 285 | regressed 0 | improved 0 | new 0 | unchanged 285]
    change:   [max +1.43M | p75 0 | median 0 | p25 -637.40K | min -10.48M]
    change %: [max +0.27% | p75 0.00% | median 0.00% | p25 -0.07% | min -1.28%]
```

Author: maksymar