feat: Add Splay Tree implementation in Python

[Vedanth-Rach]

…ue #13844

Describe your change:

This PR introduces the Splay Tree implementation in Python, resolving issue #13844.

The Splay Tree is a self-adjusting Binary Search Tree (BST) that automatically moves frequently accessed nodes closer to the root using the splay operation (a sequence of tree rotations). This ensures that recently or frequently accessed elements can be accessed rapidly again.

Implementation Details
File Location: The implementation is added under data_structures/trees/splay_tree.py.

Structure: It includes a Node class and a SplayTree class with the core logic.

Key Methods Implemented:

_rotate(self, x): Handles single left/right rotations.

_splay(self, x): The core operation, handling zig, zig-zig, and zig-zag cases.

insert(self, key): Inserts the node and splays it to the root.

search(self, key): Searches for a key and splays the accessed node (or the last accessed node if not found) to the root.

Testing: Unit tests are provided in data_structures/trees/splay_tree_test.py to cover insertion and splay behavior.

This PR resolves the request in issue #13844.

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Add or change doctests? -- Note: Please avoid changing both code and tests in a single pull request.
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
• If this pull request resolves one or more open issues then the description above includes the issue number(s) with a closing keyword: "Fixes #ISSUE-NUMBER".

[algorithms-keeper]

Closing this pull request as invalid

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