feat: Implement Fenwich Tree (Binary Indexed Tree) and Implement Additional Trie Operations

[arvinder004]

The Fenwick Tree is a data structure that efficiently calculates prefix sums and performs single element updates on an array in logarithmic time complexity (O(log n)). This makes it a valuable tool for scenarios involving frequent updates and prefix sum queries.

The FenwickTree class has been implemented with the following key methods:

init(self, size_or_array): Initializes the Fenwick Tree, allowing initialization with a specified size or from an existing array.
update(self, index, delta): Updates the value at a given index in the conceptual original array by adding delta and updates the Fenwick Tree accordingly.
prefix_sum(self, index): Calculates and returns the prefix sum up to the given index (inclusive).
range_sum(self, start_index, end_index): Calculates the sum of elements within the specified range using prefix sum operations.
get_value(self, index): (Optional utility) Returns the current value at a given index based on prefix sum differences.

Also solves #617

This pull request introduces several new functionalities to the Trie data structure, significantly enhancing its utility and completeness.

Changes:

Count of Words (count_words()): Adds a word_count attribute to the Trie class to track the number of inserted words.

Implements the count_words() method to return this count.

Longest Common Prefix (longest_common_prefix()): Implements the longest_common_prefix() method to find the longest common prefix among all words in the Trie.
Autocomplete (autocomplete(prefix)): Implements the autocomplete(prefix) method to provide a list of words matching a given prefix.
Bulk Insert (bulk_insert(words)): Implements the bulk_insert(words) method to efficiently insert multiple words.
Clear Trie (clear()): Implements the clear() method to reset the Trie.
Check if Trie is Empty (is_empty()): Implements the is_empty() method to check if the Trie is empty.
Find All Words (find_all_words()): Implements the find_all_words() method to retrieve all words.
Find the Shortest Unique Prefix (shortest_unique_prefix(word)): Implements the shortest_unique_prefix(word) method to find the shortest unique prefix for a given word.
Find the Longest Word (longest_word()): Implements the longest_word() method to find the longest word within the trie.

Tests:
Adds comprehensive unit tests for all new methods using pytest.
Ensures proper handling of edge cases and various scenarios.
Docstrings:
Provides detailed docstrings for all new methods, explaining their purpose, parameters, and return values.