Solution: remove it

Solution: rename types/variables that are inconsistent

Solution: use more descriptive names

This commit also improves comments related to some of the changes.

* Problem: radix tree's apply function uses incorrect resizing logic

Solution: rewrite the function using a vector

The buffer is extended once by 256 bytes, which will not be enough if
the node holds data larger than this number.

Solution: remove unused import and fix const placement.

* Problem: radix tree needs benchmarks and improvements

Solution: add a benchmark and make suggested improvements

subscriptions increases

Solution: use a radix tree instead of a trie to store subscriptions