Binary tree path sum (#7748)

* feat: Implement binary tree path sum (#7135)

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* Update data_structures/binary_tree/binary_tree_path_sum.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* refactor: Rename `dfs` to `depth_first_search`

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Christian Clauss <cclauss@me.com>