BST and RSA doctest (#8693)

* rsa key doctest

* move doctest to module docstring

* all tests to doctest

* moved is_right to property

* is right test

* fixed rsa doctest import

* Test error when deleting non-existing element

* fixing ruff EM102

* convert property 'is_right' to one-liner

Also use 'is' instead of '=='

Co-authored-by: Tianyi Zheng <[email protected]>

* child instead of children

Co-authored-by: Tianyi Zheng <[email protected]>

* remove type hint

* Update data_structures/binary_tree/binary_search_tree.py

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Co-authored-by: Tianyi Zheng <[email protected]>